This caramelized onion tart makes a fantastic, flavorful appetizer for your next party. Flaky puff pastry is topped with caramelized onions, gorgonzola cheese, and fresh thyme.
This caramelized onion tart is surprisingly simple - it's made with only seven ingredients. Plus, it packs a ton of flavor! This tart is topped with rich and sweet caramelized Vidalia onions and salty gorgonzola cheese.
Caramelized onions take time, so this recipe isn't a quick one. You'll need at least 35 minutes to caramelize your onions on the stove top. I promise - it's worth it!
Serve this rich, savory tart at your next holiday party as an appetizer. Perfect for Thanksgiving, Christmas, or Easter.
Ingredients and substitutions
Vidalia onions can be substituted with any sweet onions you have on hand. I used 2 large onions for this recipe, but you may need to use 3 medium onions, or 4-5 small onions.
Gorgonzola cheese can be substituted with any type of blue cheese, feta, gruyere, or goat cheese.
Beef broth can be substituted with water. However, you'll lose the extra savory flavor that beef broth adds to the onions.
How to caramelize onions
Caramelizing onions requires very little as far as ingredients are concerned. All you really need is a little olive oil and sliced onions.
As your onions cook down, you'll add a bit of beef stock for flavor, as well as salt and pepper.
Sometimes sugar is added to aid in the caramelizing process. If you'd like your tart to have a sweeter flavor, you're welcome to add a tablespoon of granulated sugar.
How will your onions look as they continue to cook down? Here's how my onions looked along the way.
1. 10 minutes.
2. 15 minutes.
3. 25 minutes.
4. 35 minutes.
Your tart can be made several hours ahead of time and served at room temperature, or reheated for a few minutes in the oven.
If you'd like to serve your tart fresh but want to save time, caramelize your onions the day beforehand. Store them in a sealed container in the refrigerator until you're ready to assemble your tart.
Caramelized Onion Tart
- 1 puff pastry sheet, thawed
- 2 tablespoons olive oil
- 2 large Vidalia onions, or other sweet onion, thinly sliced
- ¼ cup beef broth
- ¼ teaspoon salt
- ¼ teaspoon pepper
- 4 ounces gorgonzola cheese
- 1 teaspoon fresh thyme
- Preheat oven to 400 degrees and line a baking sheet with parchment paper. Set aside.
- In a saute pan over medium heat, add olive oil. When hot, add sliced onions. Cook for 10 minutes, stirring occasionally.
- Reduce heat to medium-low and add beef broth, salt, and pepper. Stir to incorporate. Cook down onions for an additional 25 minutes, stirring occasionally. If pan begins to get dry, add water 1 tablespoon at a time and lower heat slightly, scraping onions off the bottom of the pan with a spatula. Onions are done when they are a rich brown color. (You can cook down your onions up to an hour if you desire. Continue adding water, stirring and scraping your onions as needed).
- Unfold thawed puff pastry. Using a rolling pin, roll a few times each way to remove creases. Lay puff pastry onto prepared baking sheet.
- Pour onions over prepared puff pastry and spread into an even layer, leaving a 1 inch crust around the edge. Sprinkle gorgonzola cheese and fresh thyme evenly over onion layer.
- Bake for 22-25 minutes, or until crust and cheese are lightly browned and puff pastry is cooked through in the center.
- Remove from oven, slice, and serve. Tart can be served warm or at room temperature.
- Optionally, top your onion tart with fresh arugula or chopped parsley before serving.
- Gorgonzola substitutions: any blue cheese, feta (if you're opposed to the strong flavor of blue cheese), gruyere, or goat cheese.
- Caramelized onions can be prepared the day beforehand and stored in a sealed container in the refrigerator until ready to assemble tart.