Caramelized onion tart with Gruyere, bacon and thyme. (2024)

This Caramelized Onion Tart with Gruyere Cheese is a Heavenly combination of sweet and savory. With balsamic vinegar, bacon, cream and thyme … who can resist. This Savory French tart is perfect for an appetizer or a cozy light dinner served with a tossed salad.

Ingredients You’ll Need

• One pie crust to make an 8-inch tart shell.
• Sweet Onions or yellow onions.
• Bacon
• Cream
• Gruyere Cheese
• Balsamic Vinegar
• Dried Thyme
• Sugar
• Salt and Pepper

Ingredient Substitutes

• Cheese: Good substitutes for Gruyere are, Emmental, American Swiss Cheese, Comte, Fontina and Jarlsberg. Jarlsberg would be my first choice. Many caramelized onion tarts are made with goat cheese. Many don’t like the tart flavor of the goat cheese with sweet onions.
• Thyme: You most certainly can substitute fresh thyme for dried. And fresh thyme makes a nice garnish for the tart.
• Vinegar: Please no substitutes here. Balsamic is a unique, rich flavored vinegar that is important to the over all flavor of this Caramelized Onion Tart.

Pro Tip: When substituting dried herbs for fresh, a good rule of thumb is 1 Tablespoon of fresh herbs = 1 teaspoon dried herbs. Some herbs season better when used in dried form. Oregano is a good example.

Step by Step Instructions

• Step 1: Cook The Bacon: Cut the bacon into 1/2 lardons and cook in a large fry pan, stirring often until soft crispy. Remove bacon to a plate and discard all but about two tablespoon of the grease.
• Step 2: Prepare the Onions: In the meantime, cut the ends of each onion, remove skin and slice into 1/4 inch rounds.

• Step 3: Caramelize the Onions: Reduce heat medium low. Add the onions, sugar and salt and cook, stirring often until they cook down by two thirds, about 30 minutes.Add a generous 1 tablespoon pat of butter if you feel the bacon didn’t yield enough grease. Add the balsamic vinegar, reduce heat to low, and continue to cook until the onions are an even golden brown and softened, 15 more minutes.
• Step 4: Add the Cream: Remove from heat, stir in the thyme, black pepper and cooked bacon. Allow the ingredients to cool slightly. Stir the cream into the caramelized onions until thoroughly combined.

• Step 5: Fill The Pie Shell: Place the filling in the 8″ blind baked tart shell and spread it evenly with the back of a spoon.
• Step 6: Add the Gruyere Cheese. Sprinkle grated Gruyere Cheese on top.

• Step 7: Bake the tart: Bake in a 350 degree oven until the filling is set, about 15 minutes.

FAQ’s

Tips For Success

• Don’t rush the onions. It will take at least 45 minutes for them to be golden and caramelized. And don’t cook them on a higher heat. The lowest setting on the burner will create the best results.
• Slice the onions evenly so they’ll all cook the same.
• You MUST use a pie shell that has been cooked, this is called a Blind Baked Pie Shell. When making pies or tarts that call for a filling that’s already been cooked, you’ll need to blind bake the shell first. Which simply means to pre-cook the dough before adding the filling. That’s because the hour or so cooking time that it takes to bake a pie crust would over-cook the fillings, such as in this Caramelized Onion Tart Filling. This filling is already cooked, and simply needs to “set up” with a short baking time.
• Use A Homemade Pie Crust: I hope you’ll consider taking the time to make a homemade pie shell for this tart recipe. One of the great take-aways from Culinary School was how to make an All Butter Pie Crust. It’s really very easy and a skill I feel every home cook should learn. As French technique you’ll also see it referred to as pate brisee.
• Please reference my article on making a homemade pie crust for the recipe and instructions on blind baking.
• Place tart on a baking sheet to bake. Tart pans have a removable bottom. Using a sheet pan makes it easier to get it in and take it out of the oven, without disturbing that removable disk.

Leftovers and Storage

• Store cooled leftovers in a sealed container in the refrigerator for 4 – 5 days. A zip-lock bag works well here.
• You can also freeze any left over slices in a freezer safe container for up to 3 months.
• Let the tart come to room temperature to eat, or gently re-heat in the microwave or a 300 degree oven. Reheating a slice in an air-fryer keeps the crust nice and crispy.

Recipe For Caramelized Onion Tart

This caramelized onion tart recipe is delightful with flavors and textures. It’s a great appetizer to serve at a wine tasting party, or even as a starter for a special meal.

The rich, sweet aroma of slowly caramelized onions, paired with the buttery, flaky crust, creates a balance that is both comforting and sophisticated.

Whether served as an impressive appetizer at a dinner party or enjoyed as a savory treat for a cozy night in, this tart is sure to leave a lasting impression.

This caramelized onion tart is a versatile and timeless addition to any home cook’s collection. So, roll up your sleeves, embrace the art of caramelization. Cheers to creating unforgettable moments around the table with this exceptional caramelized onion tart!

More Popular Tart Recipes

We made a lot of tarts in Culinary School. Fun and rewarding, take a look at these.

And if you’re looking for more impressive appetizer ideas, don’t miss my Appetizer Category, you’ll find lots of fun recipes, including this very popular Smoked Salmon Platter.

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