Caramelized Onion Tart

This delectable onion tart is made with sweet, caramelized onions, Gruyère cheese, eggs, and a bit of cream. And using premade pie dough makes this recipe fast and easy. 

With a crispy crust and a light, thin layer of sweet onion filling, this tart is a cross between a quiche and a thin-crust French onion pizza.  It’s sure to become one of your favorite go-to party appetizer recipes. 

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Why This Recipe Works

  • It looks fancy and elegant, but it’s very easy to make.
  • It has the flavors of French onion soup, but you slice it like a pizza.
  • Although I usually serve this onion tart as an appetizer, it can also serve as a light dinner when paired with a green salad.

Recipe Ingredients

Here are the ingredients you’ll need to make this caramelized onion tart. I’ve listed a few substitutions and variations in the section below.

Be sure to check out the recipe card below for the complete list of ingredients with measurements.

Ingredients needed to make an onion tart.

Onions. Use sweet onions like Vidalia, Walla Walla, Maui Sweet, or Bermuda. Sweet onions don’t actually have more sugar than other varieties, but they have less sulfur, giving them a milder flavor. That allows you to taste more of their natural sweetness.  

Gruyère cheese. This is an aged, smooth-melting Swiss-type cheese. It’s a bit nuttier and has a more complex flavor than regular Swiss cheese, which complements the caramelized onions nicely.

Cream. You can use heavy, light, or half-and-half cream. Heavy cream makes the filling more dense and creamy.

Pie crust. The premade pie crust that you roll out works very well in this recipe. Look for it in the refrigerator section. Do not use a deep dish pie crust from the freezer because the tart is thin.

Substitutions and Variations

  • Instead of Gruyère, substitute Emmental, Jarlsberg, or regular Swiss cheese.
  • Swap puff pastry for the pie crust. It will give you a light, crackly crust that's more delicate.
  • Use low-salt beef stock to sauté the onions for a more beefy French onion soup flavor.
  • Add thinly sliced mushrooms, chopped spinach, cooked, crumbled bacon, or prosciutto over the top of the tart before you bake it.

Step-by-Step Instructions

1. Cut the onion into thin slices. Combine it with olive oil, salt, pepper, and 2 sprigs of fresh thyme in a saute pan. Saute it on medium-high heat for about two minutes, stirring to coat the onions with oil. 

Steps 1 & 2 to make an onion tart.

2. Cook the onions until caramelized. Add ¼ cup of water to the pan, cover it and cook for 10 minutes or until the onions wilt. Then, remove the lid and continue cooking the onions for an additional 15-20 minutes or until they are soft and golden. Remove the thyme stems.

3. Prepare the tart crust. Lay the pie crust over a 10-inch tart pan with a removable bottom. Gently press the dough about halfway up the sides. 

steps 3 & 4 to make an onion tart.

4. Prebake the tart crust. Line the crust with a sheet of parchment paper and place pie weights over the bottom to hold it in place. Bake the crust for 15-20 minutes or until it starts to turn golden around the edges. Remove it from the oven.

5. Prepare the filling. Whisk the eggs and cream. 

Steps 5 & 6 to make an onion tart.

6. Shred the cheese. Spread it over the prebaked crust.

7. Add onions. Spread the cooked onions evenly over the cheese.

Steps 7 & 8 to make an onion tart.

8. Add the egg and cream mixture. Gently spread it over the onions. Bake for about 30 minutes at 350ºF until golden brown.

Expert Tips!

  • Adding water to the onions helps them wilt faster and cuts down on saute time. Once they’re wilted, the water will evaporate quickly, and they’ll start to caramelize. Without this step, onions take about one hour to caramelize.
  • Scrape up any brown bits on the bottom of the pan as the onions caramelize. They’re full of sweet, delicious flavor. Add a few tablespoons of water or beef stock if they’re stuck to the bottom of the pan. They’ll scrape up easily.
  • Prebaking your tart crust will ensure it’s crispy on the bottom and not soggy. The dough will want to puff up as it cooks, so pie weights hold it in place. If you don’t have pie weights to hold it down, you can use dry beans or uncooked rice. Make sure you lay these on top of parchment paper! 

What to Eat With an Onion Tart

This tasty onion tart is perfect for a party appetizer. Pair it with a platter of grapes or fresh berries and serve it with a glass of wine, a strawberry basil shrub cocktail or mocktail, or a refreshing glass of fruited iced tea.

Depending on the size of your crowd, you can add other appetizers or snacks like:

A pan of onion tart. A spatula is lifting a slice out of the pan.

Recipe FAQs

Can you make this onion tart in advance?

This recipe is best served fresh, warm, or at room temperature. You can bake it up to two hours in advance and let it rest on the countertop. To pre[ it a day or two in advance, prebake the tart crust, grate the cheese, and refrigerate or freeze those. You can also make the custard filling a day in advance. Keep it in a separate container in the refrigerator.

How long can you store leftovers?

Store leftovers in the refrigerator for up to two days. Reheat them in the oven at 325ºF for about 15 minutes. 

Related Party Appetizer Recipes

Try some of these recipes for your next party!

Love this recipe? Please leave a 5-star rating on the recipe card below & a review in the comments section further down the page.

Recipe

An onion tart. A green napkin, forks, and fresh thyme sprigs are in the background.

Caramelized Onion Tart

An easy and elegant party appetizer
5 from 4 votes
Print Pin
Course: Appetizer
Cuisine: American, French
Diet: Lower Carb, Vegetarian
Prep Time: 40 minutes
Cook Time: 30 minutes
Total Time: 1 hour 10 minutes
Servings: 8
Calories: 250kcal

Equipment

  • 1 10-inch tart pan with removable bottom

Ingredients

  • 2 large sweet onions halved and sliced thin
  • 1 Tablespoon olive oil
  • 4 sprigs fresh thyme divided
  • ½ teaspoon kosher salt
  • teaspoon ground pepper
  • 1 premade pie crust
  • 2 large eggs
  • 3 Tbs cream
  • 5 oz Gruyere cheese shredded, 1 ½ cups

Instructions

  • Preheat oven to 375℉. Set the rack to the middle position. Spray a 10-inch tart pan with a removable bottom with cooking spray and set it aside.
  • Cut the onions into thin slices.
  • Heat the olive oil in a large saute pan over medium-high heat. Add the onions, 2 sprigs of fresh thyme, salt, and pepper, and saute for 5 minutes, stirring to coat everything well.
    Add ¼ cup of water to the onions. Cover the pan and cook the onions for 10 minutes or until wilted. Remove the lid and finish cooking the onions until they are completely soft and caramelized, about 20 minutes. Remove the thyme stems.
  • While the onions saute, press the pie crust into a 10-inch tart pan with a removable bottom pressing the crust halfway up the sides. Cover the bottom of the tart crust with parchment paper, and fill it with pie weights.
    Bake tart crust 15-20 minutes, until it starts to turn golden. Remove from oven and let cool a bit. Remove the parchment paper and pie weights when it's cool enough to handle.
  • Reduce oven temperature to 350℉.
  • Shred the cheese and add the remaining thyme leaves to the graded cheese.
  • Whisk the eggs and cream in a small bowl of measuring cup and set aside.
  • Spread grated cheese-thyme mixture evenly over the bottom of the tart crust.
    Spread caramelized onions over the cheese, covering the entire crust.
    Pour the egg-cream mixture evenly over onions. Smooth it with a spatula to ensure the crust is evenly covered.
  • Return the tart to the oven and bake for another 30 minutes at 350℉, until golden brown and the filling is set.
  • Serve warm or at room temperature.

Notes

This is best served the same day but you can store leftovers wrapped in foil in the refrigerator. Reheat in the oven at 325ºF for about 15 minutes. 
 

Nutrition

Calories: 250kcal | Carbohydrates: 17g | Protein: 9g | Fat: 16g | Saturated Fat: 7g | Polyunsaturated Fat: 1g | Monounsaturated Fat: 7g | Trans Fat: 0.01g | Cholesterol: 72mg | Sodium: 385mg | Potassium: 160mg | Fiber: 1g | Sugar: 4g | Vitamin A: 343IU | Vitamin C: 5mg | Calcium: 213mg | Iron: 1mg
Did you make this recipe?Tag me @CravingSomethingHealthy!

5 from 4 votes (4 ratings without comment)

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