This Caramelized Onion Tart makes a fantastic appetizer and is made with a handful of simple ingredients. A flaky puff pastry crust is topped with caramelized onions, gorgonzola cheese, and fresh thyme.
I don’t often venture into appetizer recipes, but I think you’ll enjoy this one. My caramelized onion tart is simple, made with only seven ingredients. Plus, it packs a ton of flavor because it’s topped rich and sweet caramelized Vidalia onions and salty gorgonzola cheese.
Caramelized onions take time, so this recipe isn’t a quick one. For this recipe, you’ll need 35 minutes to caramelize your onions on the stove top. I promise, it’s worth it!
Plus, once you’ve caramelized your onions, all you have to do is assemble your tart and it’s ready to bake. Puff pastry takes a lot of the work out of this tart recipe. It’s one of my absolute favorite ingredients when I need something done fast.
If you don’t have Vidalia onions available, any sweet onions you can find will work. I used 2 large onions for this recipe, but you may need to use 3 medium onions, or 4-5 small onions. Keep in mind, when you’re caramelizing onions, they reduce in size – a lot.
Check out my step by step photos below and see how much my onions reduced over the course of 35 minutes.
Do I need to use gorgonzola cheese? No, you’re welcome to substitute with any other similar cheese you can find. I would recommend: Any other type of blue cheese, feta (if you’re opposed to the strong flavor of blue cheese), gruyere, or goat cheese.
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, I add a bit of beef stock for flavor, as well as salt and pepper. You could also use water instead.
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. The great part about this simple recipe is that it is easily customized.
1. 10 minutes in. Now I will add beef stock, salt, and pepper to my onions.
2. 15 minutes in.
3. 25 minutes in.
4. At 35 minutes. You can continue to cook your onions down, up to an hour if you’d like.
Making a Caramelized Onion Tart
5. Spread your caramelized onions over your prepared puff pastry sheet, in an even layer.
6. Then, sprinkle with your gorgonzola cheese and fresh thyme. Now your tart is ready for the oven.
Bake for 18-20 minutes, or until the crust is browned around the edges and your cheese on top is lightly browned.
Optionally, top your onion tart with some fresh arugula or chopped parsley before serving. I sliced my tart into 9 squares, but it can be served as a smaller finger food if desired.
Caramelized Onion Tart
- 1 puff pastry sheet thawed
- 2 tablespoons olive oil
- 2 large Vidalia onions or other sweet onion, thinly sliced
- 1/4 cup beef broth
- 1/4 teaspoon salt
- 1/4 teaspoon pepper
- 4 ounces gorgonzola cheese
- 1 teaspoon fresh thyme
- Preheat oven to 400 degrees and line a baking sheet with parchment paper.
- Unfold thawed puff pastry. Using a rolling pin, roll a few times each way to remove creases. Lay puff pastry onto prepared baking sheet. 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).
- 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 18-20 minutes or until crust and cheese are lightly browned.
- Remove from oven, slice, and serve. Tart can be served warm or at room temperature.
- Optionally, top your onion tart with some fresh arugula or chopped parsley before serving. I sliced my tart into 9 squares, but it can be served as a smaller finger food if desired.
- Gorgonzola substitutions: any blue cheese, feta (if you're opposed to the strong flavor of blue cheese), gruyere, or goat cheese.