Caramelized Onion Tart

This Caramelized Onion Tart is packed with rich, savory flavor and works great as an appetizer, side dish, or even the main event. The magic comes from slowly cooking the onions until they’re perfectly caramelized and full of sweet, deep flavor. They’re spread into a flaky homemade pastry crust and topped with melty Gruyère cheese to bring it all together. It’s simple, cozy, and always a hit, whether you’re serving it at a dinner party or just treating yourself.

Ingredients to Make Caramelized Onion Tart Recipe

This homemade onion tart always feels a little fancy, but it’s surprisingly simple to make. I’m a big fan of savory pies like this, they’re perfect for a relaxed brunch, a cozy lunch, or even dinner with friends. The key to getting that amazing, rich flavor is all about patience: you’ve got to let the onions cook low and slow until they’re beautifully caramelized and sweet. Ingredients you’ll need to make Onion Tart: (Scroll down for the full printable recipe card.)

• Crust – All purpose flour, salt, salted butter and cold water form the pie dough.
• Onions – Four large Vidalia onions or yellow onions thinly sliced for the filling.
• Butter – Salted butter adds richness to the caramelized onions.
• Garlic- Enhances the flavor.
• Seasonings – Salt, sugar and black pepper. You could also add crushed red pepper flakes for spice.
• Herbs – Fresh thyme leaves adds an herbal flavor.
• Vinegar – Balsamic vinegar balances the sweetness.
• Cheese – Shredded gruyere or white cheddar cheese and chive and onion cream cheese.
• Mustard – Dijon mustard combines with the cream cheese to coat the crust and keep it from becoming soggy..
• Egg Wash – Large egg adds a golden color to the pie dough while baking. You could also brush the crust with heavy cream.
• Garnish – Grated or shredded Parmesan cheese.

How to Make the BEST Caramelized Onion Tart Recipe

• Make the Crust: Whisk together flour and salt, then use a pastry blender, cut the butter into the flour until the mixture is crumbly and the size of small peas. Add just enough water to moisten.
• Chill: Pat the dough into a disk, wrap in plastic wrap and refrigerate for at least 30 minutes or overnight.
• Make the Caramelized Onions: Cook onions and seasonings with butter until the onions cook down by half and are golden brown and tender. Add the balsamic vinegar and stir to combine.
• Heat Oven and Prepare the Pan: Line a large baking sheet with parchment.
• Roll Dough: Roll the pie dough into a 12″ circle. Transfer the pie dough to prepared parchment-lined baking sheet.
• Make Cream Cheese Mixture: Mix together Dijon and cream cheese, spread on pie dough, leaving a 2-inch border. Sprinkle with 1 cup shredded cheese.
• Layer Onions: Spoon onions over cheese then sprinkle top with reserved 1 cup shredded cheese.
• Fold Edges: Fold the outer edges of the dough over the filling to create a freeform crust.
• Brush Egg Wash on the Edges: Sprinkle Parmesan all over onions and crust.
• Oven: Bake per the cook time in the recipe until the dough is golden brown and set on the bottom.
• Serve: Let stand for 5-10 minutes, then slice into wedges and serve garnished with fresh thyme.

Kitchen Equipment to Make Onion Tart

• Large baking sheet for baking the onion tart.
• Parchment paper will keep the tart from sticking to the pan and over browning.
• Large bowl for making the crust and small bowl for the egg wash.
• A pastry blender for cutting the butter into the flour mixture.
• Measuring cups and spoons
• Sharp knife and cutting board for prepping the onions.
• A large pot, dutch oven or skillet to cook the onions.
• Cheese grater to pre the gruyere and Parmesan cheese. and a sheet pan to bake the tart.

Recipe Variations and Substitutions

• Onions: You can make this caramelized onion tart using yellow onions or red onions. Keep in mind, when cooking the onions patience is key. Depending on how vigorously they cook it will change the amount of cooking time. Adjust according to the depth of color and flavor you desire.
• Parmesan Cheese: You could use shredded Parmesan or finely grated Parmesan cheese for sprinkling on the crust.
• Cheese: I prefer the nutty flavor of Gruyere cheese for this recipe. That being said, you could adapt the flavor using a sharp white cheddar cheese, swiss cheese or Asiago cheese. You could also use a cheese blend that you enjoy.
• Pie Crust Shortcut: You could adapt this recipe using thawed puff pastry or two refrigerated crusts rolled together to form a thicker crust.
• Fresh Herbs: You could use fresh parsley or fresh chives in place of thyme.
• Pan Options: This tart is somewhat like a savory galette popularly made with sweet pie and fruit fillings. It’s a free form pie and doesn’t require a special pan to bake it. That being said, you could adapt this recipe using a 10-inch tart pan with a removable bottom, pie pan or 9×9-inch pan.

Storage and Leftovers

• Make-Ahead Tip: The french onions mixture for the filling can be prepared one day in advance and placed into an airtight container and chilled until assembling the tart to bake.
• Crust Tip: When making the pastry, it’s important to allow it rest time to chill and firm the butter in the crust. Doing so will allow the butter to melt slowly while baking and create steam for a flaky texture and pleasing end result. The crust can be made up to 2 days in advance and stored chilled.
• Leftovers: Store leftover Caramelized Onion Tart wrapped in aluminum foil or in an airtight container chilled in the refrigerator for up to 3 days.
• Reheating: Reheat pieces in single servings in the microwave or on a sheet pan in a 350°F oven for a few minutes just until heated through. If it begins to brown lay a piece of aluminum foil on top.

More Savory Pie Recipes to Make

• Plum Tomato Tart is another option that has several severing options. Enjoy it as a lighter entree, side dish or appetizer.
• Bacon and Onion Bistro Tart was inspired by my favorite corner bistro from College.
• Fresh Tomato Tart with Basil Pesto and Fontina Cheese is packed with fresh summer flavors.
• Double Crust Chicken Pot Pie is comfort food 101.
• This recipe for Broccoli Cheese Quiche with Bacon forms its own crust while baking.
• Treat the family to a Chicken Pot Pie Crescent Ring for supper any day of the week.
• Beef and Potato Galette from A Foodie Affair.

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Helpful Kitchen Items:

• Sheet Pan
• Measuring Set
• Kitchen Utensils
• Knives and Chopping Board