Caramelized Onion Tart

Why You’ll Love This Recipe

This tart is all about bold flavor and elegant simplicity. Caramelizing onions brings out their natural sweetness and umami, making them the star of the show. It’s a versatile dish—serve it warm, cold, or at room temperature—and it works beautifully as an appetizer, brunch item, or light main course. You can make it with store-bought pastry to save time or go fully homemade for a special touch.

Ingredients

(Tip: You’ll find the full list of ingredients and measurements in the recipe card below.)

• Yellow or sweet onions (thinly sliced)
• Olive oil or butter
• Salt
• Sugar (optional, to enhance caramelization)
• Fresh thyme or rosemary (optional)
• Puff pastry or shortcrust pastry (store-bought or homemade)
• Eggs
• Heavy cream or sour cream (optional for a custard base)
• Grated cheese (optional – such as Gruyère, goat cheese, or Parmesan)
• Black pepper

Directions

1. Preheat your oven to 375°F (190°C).
2. In a large skillet, heat olive oil or butter over medium-low heat. Add the sliced onions and a pinch of salt.
3. Cook slowly, stirring often, for 30–40 minutes until onions are golden brown and soft. Add a pinch of sugar halfway through if desired.
4. Stir in herbs like thyme or rosemary in the last few minutes of cooking. Set aside to cool slightly.
5. Roll out your pastry and press it into a tart pan or baking sheet. Prick the base with a fork.
6. In a bowl, whisk eggs with cream (if using) and season with salt and pepper.
7. Spread the caramelized onions over the pastry base. If using, sprinkle cheese over the onions.
8. Pour the egg mixture over the filling if you’re making a custard-style tart.
9. Bake for 25–30 minutes, or until the crust is golden and the filling is set.
10. Let cool slightly before slicing. Serve warm or at room temperature.

Servings and timing

This recipe yields 6–8 servings. Total time is approximately 1 hour and 15 minutes: about 40 minutes for caramelizing onions and 30–35 minutes for baking and prep.

Variations

• Cheese lovers: Add goat cheese, Gruyère, or blue cheese for extra richness.
• Rustic galette style: Skip the tart pan and fold the edges of the dough over the filling.
• Vegan option: Use dairy-free pastry and skip the egg/cream mixture, adding herbs and vegan cheese instead.
• Add veggies: Layer in sautéed mushrooms, roasted red peppers, or spinach.
• Mini tarts: Use muffin tins or mini tart pans for individual portions.

Storage/Reheating

Store leftovers in an airtight container in the refrigerator for up to 3 days. Reheat in a 350°F oven for 10–15 minutes to restore crispness. Avoid microwaving to keep the crust from getting soggy. The tart can also be frozen and reheated straight from the freezer.

FAQs

What’s the best onion to use for caramelizing?

Yellow or sweet onions work best due to their natural sugars and balanced flavor.

Can I make this tart ahead of time?

Yes, it can be fully baked and stored in the refrigerator. Reheat in the oven before serving.

Do I need to use cream and eggs?

No, you can make a dairy-free version by omitting them or using plant-based alternatives.

Can I use store-bought pastry?

Absolutely. Puff pastry or pie dough both work well and save time.

Why are my onions not caramelizing?

Low heat and patience are key. Avoid turning the heat too high, and stir often over 30–40 minutes.

Can I freeze caramelized onion tart?

Yes, cool it completely before freezing. Wrap tightly and freeze for up to 2 months. Reheat in the oven from frozen.

What herbs go well in this tart?

Thyme, rosemary, sage, or even a sprinkle of oregano add beautiful flavor to the onions.

Can I make this gluten-free?

Yes, use a gluten-free pastry dough. The filling is naturally gluten-free.

What can I serve with onion tart?

A green salad, roasted vegetables, or a light soup pair well with this savory tart.

Is this tart good cold?

Yes, it can be served cold or at room temperature, making it perfect for picnics or meal prep.

Conclusion

Caramelized Onion Tart is a deliciously rich and satisfying dish that turns simple ingredients into something truly special. With its flaky crust and sweet-savory filling, it’s perfect for any occasion—from brunch gatherings to cozy weeknight dinners. Easy to prepare and endlessly customizable, this tart is sure to become a favorite in your kitchen.

Caramelized Onion Tart

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Caramelized Onion Tart is a savory pastry made with sweet, slow-cooked onions layered over a buttery crust. Enhanced with herbs and optional cheese or cream, it’s a versatile dish perfect for brunch, lunch, or as a starter.

• Author: Laura
• Prep Time: 15 minutes
• Cook Time: 55 minutes
• Total Time: 1 hour 10 minutes
• Yield: 6–8 servings
• Category: Appetizer / Main
• Method: Baking
• Cuisine: French / European
• Diet: Vegetarian

Ingredients

• 3–4 large yellow or sweet onions, thinly sliced
• 2 tablespoons olive oil or butter
• 1/2 teaspoon salt
• 1/2 teaspoon sugar (optional)
• 1 teaspoon fresh thyme or rosemary (optional)
• 1 sheet puff pastry or shortcrust pastry (store-bought or homemade)
• 2 eggs (optional, for custard filling)
• 1/3 cup heavy cream or sour cream (optional)
• 1/2 cup grated cheese (Gruyère, goat cheese, or Parmesan, optional)
• Black pepper, to taste

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Instructions

1. Preheat oven to 375°F (190°C). Roll out pastry and fit it into a tart pan or onto a baking sheet. Prick the base with a fork and chill while preparing filling.
2. Heat oil or butter in a skillet over medium-low heat. Add sliced onions and salt. Cook slowly for 30–40 minutes, stirring often, until golden and caramelized. Add sugar halfway through to enhance caramelization, if using.
3. Add herbs during the last few minutes of cooking. Set onions aside to cool slightly.
4. If using, whisk eggs and cream together in a small bowl. Season with salt and pepper.
5. Spread the caramelized onions evenly over the pastry. Sprinkle with cheese if desired. Pour egg mixture over the top for a custard-style tart.
6. Bake for 25–30 minutes, or until the pastry is golden and the filling is set.
7. Cool slightly before slicing. Serve warm or at room temperature.

Notes

• Onions must be cooked low and slow to develop deep flavor—don’t rush the caramelization process.
• Puff pastry gives a light, flaky base; shortcrust pastry makes for a sturdier, buttery tart.
• This tart can be made without eggs or dairy for a vegan version—just skip the custard base and cheese.
• Pairs well with salad, soup, or served as part of a brunch spread.

Nutrition

• Serving Size: 1 slice
• Calories: 230
• Sugar: 6g
• Sodium: 270mg
• Fat: 15g
• Saturated Fat: 6g
• Unsaturated Fat: 8g
• Trans Fat: 0g
• Carbohydrates: 18g
• Fiber: 2g
• Protein: 5g
• Cholesterol: 55mg