Rustic Onion Tart

Rustic onion tart with caramelized red onions, Gruyere cheese, and a butter crust.

  • Prep time: 20 minutes
  • Cook time: 1 hour, 40 minutes
  • Yield: Serves 4


  • 1 recipe for butter sour cream pastry dough* or 1 packaged, flat pie crust (Trader Joe's has one in their frozen section)
  • 3 medium sized red and/or yellow onions (enough for 5 to 8 cups, sliced)
  • 2 tablespoons extra virgin olive oil
  • 1 tablespoon butter
  • Salt
  • 1 teaspoon balsamic vinegar
  • 1/2 teaspoon fresh thyme, chopped, or 1/4 teaspoon dried thyme
  • 3/4 cup (not packed) roughly grated Gruyère Swiss cheese

*Sour cream pastry dough:

  • 1 1/4 cup (160 g) all purpose flour
  • 1 teaspoon salt
  • 5 ounces of butter (1 1/4 sticks, 10 Tbsp, 137g), cubed
  • 1/4 cup sour cream


1 Prepare the dough: If you are making a crust from scratch, prepare the dough and let it chill in the refrigerator while you are cooking the onions.

To prepare the dough, whisk the flour and salt together in a large bowl. Cut the butter into the flour with your hands or with a pastry cutter, until the mixture resembles a coarse meal.

Add the sour cream and use a fork to incorporate it into the dough. Gather the dough into a ball and shape it into a disk. Wrap it with plastic wrap and chill for at least an hour.

2 Peel and slice the onions, lengthwise from stem to root. (See How to Slice an Onion)

3 Caramelize the onions: Heat olive oil and butter in a large, heavy-bottomed sauté pan on medium heat. Once the butter has melted, add the onions and sprinkle a little salt over them.

Cook, stirring occasionally for 10 minutes, until the onions have softened and are translucent.

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Reduce the heat to medium low and cook for an additional 40 minutes, stirring occasionally, until the onions are well browned.

Add balsamic vinegar and cook for 10 minutes more, until onions are completely caramelized. Remove from heat.

4 Roll out the dough: Preheat the oven to 450°F. Remove the dough from the refrigerator and let stand for 5 minutes before rolling it out.

Roll out the dough on a lightly floured surface to a 13-inch diameter. Transfer the crust dough to a cookie sheet lined with parchment paper.

5 Layer the cheese and onions onto the dough: Place all but a couple tablespoons of the cheese in the center of the dough. Spread to within 1 1/2 inches from the edges. Add the caramelized onions, layering them on top of the cheese. Sprinkle with thyme.

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6 Pleat the edges: Fold the edges of the crust dough over so that a small circle of onion is still showing in the centre of the tart. Sprinkle the remaining cheese over the top of the tart.

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7 Bake: Place in the oven on the middle rack. Bake for 10 minutes at 450°F. Reduce the heat to 350°F and bake for an additional 20-25 minutes, until the crust is golden brown.

Remove from oven and let sit for 10 minutes before serving.

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  • Karen

    Hi what other cheeses can you use?

    • Elise Bauer

      Hi Karen, you could substitute with grated Comté, Emmentaler, or Gouda. Or you could sprinkle with a little blue cheese, goat cheese (chevre) or feta.

  • Angela

    I love this tart, it’s fabulous, a crowd pleaser! I’d like to freeze it, could you tell me if it is best to freeze it before baking or already baked? Thanks.


    • Emma Christensen

      Hi, Angela! We haven’t tried freezing this tart, but my instincts say that it should do just fine. You should be able to freeze either the baked or unbaked tart — wrap it tightly in foil, then in plastic wrap or a freezer zip-top bag, and then freeze for up to a month. No need to thaw before baking or re-heating. Let us know how it works out!

  • Janet

    Hi, ingredients for Trader Joe’s frozen pie crusts include palm oil and butter. The crust is high in total fat (13 grams) and saturated fat (7 grams) and is extremely crumbly even when carefully thawed and unrolled. Be ready to do a lot of surgery patching it together.

  • Jane

    The sour cream pastry was great. Instead of one large one, I use a large glass to cut circles and made individual appetizers. They were a great hit.


  • Mari Anne Souza

    We have a winner! Made 2 of these for Christmas Eve, to go along with other appetizers. Everybody loved them. I used the pre-made pillsbury dough. I’m going to try it with puff pastry. Thank you, very much!


  • Joan

    Since I made this only for myself as a test yesterday – I have lots of leftovers. I just popped a piece of the tart in the microwave today and all I can say is: Did I really make that? :) I don’t know what it is – but the day I’m cooking, I truly have a hard time knowing the full impact of a dish’s flavors. Probably comes from working with the food too much. I only wish I could eat the entire thing…right now; that good. My only concern yesterday was seeing how very rich the pastry was…But – as a treat – what the heck. My friends are going to love your recipe. You KNOW I do.


  • Marisa

    This is so easy and forgiving. I’ve made this several times but one day dinner plans changed. I assembled and placed in the fridge for 2 days! Baked it and it tasted just as good as all the other times. Now I make it 1 day in advanced for dinner parties, delish.


  • tt

    Can a store bought puff pastry replace the pie crust?

    If I were to use puff pastry, I wouldn’t fold it over the center like you do with a regular pie crust round. I would pile the filling on top of the puff pastry, just up to an inch from the edge. ~Elise

  • Lianne

    Can the onions be carmelized the day before and refridgerated, then put in the crust & baked the next day?

    Yes. ~Elise

  • Wunderkind

    A friend recommended I try this recipe, and I love it! I’m not a big fan of Gruyère cheese, or balsamic vinegar, so I left both out and just added some sugar to the onions. My mom loved it so much she had me bake a ton of mini tarts for her birthday party.

    I’ve found that onions also taste quite good on pizza bases with a bit of a pizza tomato sauce and roasted baby tomatoes. To counterbalance the sweetness I added some blue Danish cheese just before the whole thing went into the oven.

  • JBJ

    This was GREAT! Words cannot express. I changed it up a little and used Pilsbury cresent rolls as my crust and it worked just as well and quicker. Now a favorite!

  • Gayle

    I made three of these tarts for Christmas dinner with the family. I used a mix of sweet onion and red onion, and a purchased whole wheat crust for one tart and regular crusts for the other two. If I heard it once I heard it 20 times: “This is the best thing we’ve had tonight! You have to make this for every family gathering from now on!” They were fighting over who could take some home – someone hid most of a tart for himself. Anyway, it’s a great recipe: simple and flexible. Use other cheeses than gruyere if you like (I did). I may add a small layer of other vegetables and/or seasoned ground meat to make it more of a meal…

  • JT

    Delish. Just finished and tested. Beautiful to boot. Easy. Been hankering to make this for some time. Today was the day. Definitely making for friends as a prelude to chicken marsala. Used Gruyère (missed the Swiss cheese part)…but was very tasty. Trader Joe’s crust. (I put the tart on a few paper towels while cooling to drain some of the butter from the crust.) Only thing I would recommend would be to try the carmelized onions before putting in the crust and adjust to taste. Thanks, Elise…I love looking like a pro!!

  • Grace

    This has become a favourite in my family after only one appearance (for my mom’s 60th birthday)–and now its going to make an encore performance for Thanksgiving. I just carmelized my onions and will soon set to making my mom’s recipe for a “water-whip” pie crust that we all dearly love. I’m planning to freeze it tonight (as per margaret’s direction above) and then thaw it tomorrow morning and toss it into the oven in time for it to come out just before the turkey and act as our appetizer. Thanks for the new family favourite! I’m passing this one on to my kids (that I don’t have yet). :)

  • Not that Carrie, the other Carrie

    This sounds absolutely amazing, but has anyone ever tried it with other than red onions?

    I have such a problem with them, I think they smell like b.o. *shakes head* don’t ask, I have no clue.

    What about a big mound of Vidalia or just yellow and whites?

    You can easily make this with other types of onions. Go for it! ~Elise

  • margaret

    I have doubled this and saved one in the freezer, swathed in its parchment paper and then snugged in foil. I took it out and let it come to room temp then popped it in the oven. It was just as good as the freshly made. You can also roast the onion in the oven if you can’t tend the stove.

  • Sarah

    Could I put this together for a party and let it sit in the fridge for an hour or so before baking?
    Also, if I wanted to add a little meat to this would you reccomend a sweet italian sauasage or prosciutto?
    Thanks, it looks like an easy summer beauty.

    I don’t think there would be a problem with letting this sit in the fridge for an hour before baking. Regarding meat, both Italian sausage and prosciutto sound like delicious additions. ~Elise

  • Erin

    This was truly divine! Cheated and used a store bought dough, but a using cave-aged gruyere more than made up for it. Thanks for a fabulous recipe that I’ll be sure to make again and again.

  • cheryl

    Anyone know of a good gf crust that can be used for the tart?



  • Liz

    This was absolutely fantastic, and so easy! You really can’t go wrong with caramelized onions and gruyere– so delicious! I think this will be a go-to dish when I need a quick savory appetizer.

  • Laura

    This is a rich, delicious tart. I made the onions the day before, assembled and baked the tart the next morning and reheated it just before serving. Obviously this is a forgiving recipe and a much appreciated one as well. Thank you!

  • Marianne

    Elise, I made this tonight and it was really wonderful! I’m writing it up as we speak–thanks for the recipe.

  • Mark

    I’m always looking for any new and different recipies with onions and boy was this different. Enough to be a favorite when people come over. Love it!

  • art-sweet

    An awful lot of the premade pie crusts still use lard (buh-bye vegetarian recipe, hello stomach cramps all night long). Anyone know of a good one that doesn’t? Does the TJ’s crust have lard in it?

  • Alanna

    Gorgeous … with the addition of maybe a tablespoon or two of brown sugar, this is how I cook (and cook and cook and cook) onions for fajitas. I’m curious: have you tried the Trader Joe’s pie crust?