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Home » Recipes » Appetizers

Caramelized Onion Tart

Modified: May 21, 2024 · Published: Jul 16, 2019 by Heather · As an Amazon Associate I earn from qualifying purchases. · 938 words. · About 5 minutes to read this article.

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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.

Caramelized onion tart sliced into squares.

This caramelized onion tart is surprisingly simple to prepare. It's topped with rich and sweet caramelized Vidalia onions and salty gorgonzola cheese - a total crowd pleaser!

Caramelized onions take time, so this recipe isn't a quick one. You'll need at least 45 minutes to caramelize onions properly on the stovetop, but the end result is totally worth it!

Serve this rich, savory tart at your next holiday party as an appetizer. It's perfect for Thanksgiving, Christmas, and Easter.

Ingredients and substitutions

Ingredients on a counter top.
  • Puff pastry - You'll need one sheet of thawed puff pastry. Homemade puff pastry also works.
  • Oil - I used olive oil for this recipe. If needed, it can be substituted with your favorite cooking oil.
  • 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 if needed, but you'll lose the extra savory flavor that beef broth adds to the onions.
  • Seasoning - Salt, pepper, and fresh thyme add a mild, savory flavor to the tart.

Tips and tricks

Onions caramelizing in a pan over time.

Visual cues while caramelizing onions - How will your onions look as they continue to cook down? See the photo above: (1) after 10 minutes of cooking, (2) 15 minutes, (3) 25 minutes, and (4) 35 minutes.

Low and slow - Keep your heat low to allow onions to cook without burning. Looking dry? Add a splash of water, reduce the heat slightly, and scrape the bottom of the pan to release any stuck onions.

Trust the process - Caramelizing onions takes time. Resist the urge to turn up the heat or use par-cooked onions on your tart. The process of caramelizing onions adds an immense amount of flavor to the finished dish that is worth the time and effort.

Blind bake your puff pastry - Don't skip this step. Blind baking sets the top and bottom of your puff pastry, which helps prevent it from getting soggy once the toppings have been added.

Storage

Caramelized onions can be made ahead and stored in the refrigerator for up to a week.

Your prepared tart will keep in the refrigerator for up to 3 days.

Frequently asked questions

Caramelized onion tart on a sheet pan.
Can this be made ahead?

Caramelized onions can be prepared up to a week ahead of time and stored in the refrigerator until you're ready to assemble your tart. Puff pastry tarts are best served within a few hours of baking. Once refrigerated, your puff pastry will soften and lose its crisp texture.

How can I caramelize my onions faster?

There's not really a great way to caramelize onions faster. Simply turning up the heat can burn onions before they caramelize properly. I like to add a bit of liquid in the form of beef broth, which not only adds flavor but also steams the onions and helps them cook a bit faster. However, your onions will take at least 35-45 minutes to cook, so account for this in your prep time. Caramelized onions will keep in the refrigerator for up to a week, so this part of the recipe can be prepped well in advance.

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📖 Recipe

Caramelized onion tart sliced into squares.
Print Recipe
4.67 from 3 reviews

Caramelized Onion Tart

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.
Prep Time40 minutes minutes
Cook Time18 minutes minutes
Total Time58 minutes minutes
Servings: 9 servings
Calories: 246kcal
Author: Heather

Ingredients

  • 1 puff pastry sheet, thawed
  • 2 tablespoons olive oil
  • 2 large Vidalia onions, thinly sliced
  • ¼ cup beef broth
  • ¼ teaspoon salt
  • ¼ teaspoon pepper
  • 4 ounces gorgonzola cheese
  • 1 teaspoon fresh chopped thyme
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Instructions

  • In a sauté pan over medium heat, add olive oil. When hot, add sliced onions. Cook for about 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 35 minutes, stirring occasionally, or until caramelized to your liking. If pan begins to get dry, add water, 1 tablespoon at a time, and lower heat slightly. Onions are done when they look rich brown in color. Remove from heat and set aside.
  • Preheat oven to 400 degrees Fahrenheit and line a baking sheet with parchment paper. Set aside.
  • Unfold thawed puff pastry. Using a rolling pin, roll out your puff pastry sheet into about a 12 inch square and place onto your baking sheet. Bake for 15 minutes and remove from oven. If your puff pastry is very puffy, gently press down with a paper towel to deflate.
  • 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 about 15 minutes more, 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.

Equipment Recommendations

  • Wooden Rolling Pin
  • Nordic Ware Half Baking Sheet
  • Reynolds Parchment Paper
  • Stainless Steel Saute Pan

Notes

  • Time saver - Caramelized onions can be prepared up to a week beforehand and stored in a sealed container in the refrigerator until ready to assemble.
  • Onions can be caramelized for up to an hour or more for a deep, rich flavor. Continue adding a splash of water as needed and cook as long as you'd prefer.
  • Leftover tart can be stored in the refrigerator for up to 3 days. 

Nutrition Estimate

Serving: 1square | Calories: 246kcal | Carbohydrates: 18g | Protein: 5g | Fat: 17g | Saturated Fat: 5g | Cholesterol: 9mg | Sodium: 339mg | Potassium: 136mg | Fiber: 1g | Sugar: 4g | Vitamin A: 105IU | Vitamin C: 3.9mg | Calcium: 84mg | Iron: 1mg
Course: Appetizer
Cuisine: American

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Heather of The Toasty Kitchen

Hi, I'm Heather!

I love cooking with simple, everyday ingredients and want to help you make homemade meals with ease.

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