Caramelized Onion Tart

Sweet, savory, and utterly irresistible, this Caramelized Onion Tart is the ultimate blend of rich flavors in a buttery, flaky crust. Made with golden, slow-cooked onions, creamy cheese, and a hint of herbs, it’s perfect as a brunch centerpiece, a starter for dinner parties, or even a light lunch with a side salad. Elegant yet simple to make, this tart is proof that a few quality ingredients go a long way.

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Why You’ll Love This Recipe
Rich & Elegant – Caramelized onions add natural sweetness and depth.
Buttery & Flaky Crust – A tender pastry base that holds everything beautifully.
Perfect for Any Occasion – Brunch, lunch, or party appetizer.
Customizable – Add herbs, cheese, or your favorite toppings.
Make-Ahead Friendly – Prep the filling or crust in advance for easy assembly.

Ingredients You’ll Need

For the Tart Crust (or use store-bought puff pastry):

• 1¼ cups all-purpose flour
• ½ tsp salt
• ½ cup cold unsalted butter, cut into cubes
• 3–4 tbsp ice water

For the Caramelized Onion Filling:

• 3 large yellow onions, thinly sliced
• 2 tbsp olive oil
• 1 tbsp unsalted butter
• ½ tsp salt
• ½ tsp sugar (helps speed up caramelizing)
• 1 tsp fresh thyme leaves (or ½ tsp dried thyme)
• ¼ tsp black pepper
• ½ cup whole milk or heavy cream
• 2 large eggs
• ¾ cup shredded gruyère or mozzarella cheese
• Optional: 1 tsp Dijon mustard (for a tangy depth)

Tools You’ll Need

• Tart pan (9-inch) or pie dish
• Rolling pin (if making crust from scratch)
• Large skillet
• Mixing bowls
• Whisk
• Baking sheet (to catch drips)

Step-by-Step Instructions

Step 1: Make the Tart Crust (Skip if Using Puff Pastry)
In a large bowl, mix flour and salt.
Cut in cold butter using a pastry cutter or fork until the mixture resembles coarse crumbs.
Add ice water one tablespoon at a time, mixing gently, just until dough holds together.
Shape into a disc, wrap in plastic, and chill for at least 30 minutes.

Step 2: Caramelize the Onions
In a large skillet, heat olive oil and butter over medium heat.
Add sliced onions, salt, sugar, and thyme.
Cook slowly for 30–40 minutes, stirring occasionally, until onions are soft, golden, and deeply caramelized.
Remove from heat and let cool slightly.

Step 3: Prepare the Crust
Preheat oven to 375°F (190°C).
Roll out chilled dough on a floured surface and press into a tart pan. Trim the edges.
Prick the bottom with a fork, line with parchment paper, and fill with pie weights or dried beans.
Blind bake for 12 minutes, remove weights, then bake for another 5 minutes until lightly golden.
Let cool slightly.

Step 4: Make the Egg & Cheese Mixture
In a bowl, whisk together eggs, milk (or cream), black pepper, and mustard if using.
Stir in the grated cheese.

Step 5: Assemble the Tart
Spread caramelized onions evenly over the bottom of the pre-baked crust.
Pour the egg mixture on top, spreading evenly.
Top with a sprinkle of extra cheese or fresh thyme if desired.

Step 6: Bake the Tart
Bake in the preheated oven for 25–30 minutes, or until the filling is set and lightly golden on top.
Cool for 10 minutes before slicing and serving.

Tips for Success
Low & Slow for Onions – Patience makes perfect caramelized onions. Don’t rush the process.
Use Cold Butter – Keeps the crust flaky and tender.
Blind Bake the Crust – Prevents soggy bottoms and helps the crust stay crisp.
Let It Rest – Allow the tart to cool slightly before cutting for cleaner slices.
Add a Twist – Crumbled feta, goat cheese, or roasted garlic make great additions.

Serving Suggestions
With a Green Salad – Arugula or spinach salad with a lemon vinaigrette pairs beautifully.
As a Starter – Cut into wedges or squares and serve at room temperature.
Brunch Platter – Serve alongside fresh fruit, croissants, and tea.
With Soup – Pair with a creamy soup like butternut squash or tomato bisque.

How to Store & Reheat

Storing:
Refrigerate: Store leftovers in an airtight container for up to 4 days.

Freezing:
Wrap tightly and freeze baked tart for up to 2 months. Thaw overnight before reheating.

Reheating:
Oven: Warm at 325°F (160°C) for 10–15 minutes until heated through.
Avoid microwaving to maintain crisp crust.

Frequently Asked Questions

1. Can I make this tart ahead of time?
   Yes! You can caramelize the onions and even bake the crust a day ahead. Assemble and bake just before serving.
2. Can I use puff pastry?
   Absolutely. Puff pastry works great and saves time. Just roll it out and press into your tart pan.
3. What cheese works best?
   Gruyère adds a nutty depth, but mozzarella, fontina, or even cheddar are tasty alternatives.
4. Can I make it egg-free?
   Try a dairy-free béchamel or cashew cream as a binder instead of eggs.
5. What other toppings can I add?
   Sliced tomatoes, sautéed mushrooms, or spinach pair wonderfully with caramelized onions.

Final Thoughts
This Caramelized Onion Tart is a beautifully simple yet sophisticated dish that brings out the best in sweet onions and savory cheese. With its rich flavor and golden crust, it’s perfect for entertaining or elevating your everyday meals. Make it your own with creative additions or enjoy its pure, timeless goodness as-is.

Give it a try and let me know how it turned out! Leave a review, share your photos online, and inspire others to cook deliciously at home.

Preparation Time: 20 minutes
Cooking Time: 30 minutes (plus 30–40 mins for caramelizing onions)
Cuisine: French-Inspired

Nutritional Information (Per Serving):
Calories: 310 | Protein: 9g | Carbohydrates: 25g | Fat: 20g | Fiber: 2g | Sodium: 300mg

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