The Ultimate Makeover: Onion Tart Recipe

Introduction

This ultimate makeover onion tart transforms simple red onions into a rich, caramelized filling nestled in a crisp, homemade pastry. It’s a comforting yet elegant dish perfect for lunch, dinner, or entertaining guests.

Ingredients

• 2 large red onions (550g/1lb 4oz total weight), halved lengthways
• 2 tbsp rapeseed oil
• 2 medium eggs
• 200ml carton half-fat crème fraîche
• 1 tsp thyme leaves
• 1 tsp Dijon mustard
• 25g Gruyère cheese
• 175g self-raising flour
• 25g cold butter, cut in small pieces
• 100g natural yogurt
• 4 tbsp semi-skimmed milk

Instructions

1. Step 1: Slice the onions into small, thin, wedge-shaped pieces. Heat the rapeseed oil in a large non-stick sauté or deep frying pan over medium heat. Add the onions and fry for about 20 minutes, stirring occasionally to allow them to caramelize and become sticky.
2. Step 2: Meanwhile, preheat the oven to 190°C (170°C fan/gas mark 5) and place a baking sheet inside to heat. In a bowl, combine the self-raising flour, cold butter, and a pinch of salt. Rub with your fingers until the mixture resembles rough crumbs.
3. Step 3: Mix the natural yogurt and semi-skimmed milk together, then pour this into the flour mixture. Use a knife to bring the dough together briefly, then remove from the bowl and gently press into a ball without overworking.
4. Step 4: Roll out the dough thinly on a lightly floured surface. Use it to line a 23cm round, fluted, loose-based flan tin about 2.5cm deep, pressing the dough into the flutes with your fingers. If sticky, dust your fingers with flour.
5. Step 5: Beat the eggs in a medium bowl. Stir in the crème fraîche, thyme leaves, Dijon mustard, and season with pepper.
6. Step 6: Spread half of the caramelized onions over the tart base, season with pepper, and scatter half the Gruyère over them. Pour the egg mixture over, then top with the remaining onions and cheese.
7. Step 7: Place the flan tin on the hot baking sheet and bake in the oven for 25-30 minutes until the base is cooked and the filling is set and golden.
8. Step 8: Remove from the oven and cool for about 10 minutes. Carefully remove the tart from the tin and serve warm for the best flavor.

Tips & Variations

• For extra depth, add a splash of balsamic vinegar to the onions while caramelizing.
• Substitute Gruyère with Emmental or mature cheddar for a different cheesy flavor.
• If you prefer a crisper crust, blind bake the pastry base for 10 minutes before adding the filling.
• Add fresh herbs like rosemary or parsley for a fragrant twist.

Storage

Store any leftover tart in an airtight container in the refrigerator for up to 2 days. Reheat gently in a low oven (about 160°C) to keep the pastry crisp and the filling warm. This tart is best enjoyed fresh but can also be served cold for a picnic or packed lunch.

How to Serve

Serve this delicious recipe with your favorite sides.

FAQs

Can I use a different type of onion?

Yes, you can use yellow or white onions, but red onions provide a lovely sweetness and color when caramelized that’s ideal for this tart.

Is it possible to make the dough ahead of time?

Absolutely. You can prepare the dough a day in advance and keep it wrapped in the refrigerator. Bring it to room temperature before rolling out.

The Ultimate Makeover: Onion Tart Recipe

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★★★★★

4.9 from 90 reviews

• Author: Jack
• Total Time: 55 minutes
• Yield: 6 servings 1x

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Description

This ultimate onion tart recipe features sweet, caramelized red onions layered in a creamy, thyme-infused egg and crème fraîche filling, all nestled in a delicate, flaky yogurt-based pastry crust. Baked to golden perfection with Gruyère cheese, this savory tart is a perfect light meal or an impressive appetizer that’s simple to prepare and bursting with rich, comforting flavors.

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Ingredients

Scale 1x2x3x

Onion Filling

• 2 large red onions (550g/1lb 4oz total weight), halved lengthways
• 2 tbsp rapeseed oil
• 25g Gruyère cheese, grated
• 1 tsp thyme leaves
• 1 tsp Dijon mustard
• Salt and pepper, to taste

Base (Pastry)

• 175g self-raising flour
• 25g cold butter, cut into small pieces
• 100g natural yogurt
• 4 tbsp semi-skimmed milk

Filling Mixture

• 2 medium eggs
• 200ml carton half-fat crème fraîche

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Instructions

1. Caramelize the Onions: Slice the halved red onions into small, thin, wedge-shaped pieces. Heat 2 tablespoons of rapeseed oil in a large, preferably non-stick, sauté or deep frying pan over medium heat. Add the onions and cook for approximately 20 minutes, stirring only occasionally, allowing them to caramelize slowly and become sticky and golden brown.
2. Prepare the Pastry Base: Preheat the oven to 190°C (170°C fan)/Gas mark 5 and place a baking sheet inside to heat. In a bowl, combine 175g self-raising flour, 25g cold butter, and a pinch of salt. Rub the butter into the flour with your fingers until the mixture resembles rough crumbs. Mix together 100g natural yogurt and 4 tablespoons semi-skimmed milk, then pour this liquid into the flour mixture. Use a knife to briefly combine the ingredients until the dough just comes together. Remove the dough from the bowl and gently press it into a ball without overworking it.
3. Roll and Line the Tin: On a lightly floured surface, roll out the dough thinly. Use it to line a 23cm round, fluted, loose-based flan tin about 2.5cm deep, pressing the dough gently into the flutes with your fingers. If the dough feels sticky, lightly dust your fingers with flour. Place the tin on the heated baking sheet to help the base cook evenly.
4. Prepare the Filling Mixture: In a medium bowl, beat 2 eggs thoroughly. Stir in 200ml of half-fat crème fraîche, 1 teaspoon thyme leaves, 1 teaspoon Dijon mustard, and season with salt and pepper to taste. Mix until well combined.
5. Assemble the Tart: Spoon and spread half of the caramelized onions evenly over the prepared pastry base. Season with freshly ground black pepper and scatter half of the grated Gruyère cheese on top. Pour the egg and crème fraîche mixture over the onions and cheese layer evenly. Then scatter the remaining caramelized onions and the remaining Gruyère on top.
6. Bake the Tart: Place the flan tin carefully onto the hot baking sheet in the preheated oven. Bake for 25-30 minutes, or until the pastry base is cooked through and the filling is set and slightly golden on top.
7. Cool and Serve: Remove the tart from the oven and allow it to cool for about 10 minutes to set. Then carefully remove it from the tin and serve warm to enjoy the fresh, rich flavors at their best.

Notes

• Be patient when caramelizing the onions for best flavor and texture, stirring only occasionally.
• Do not overwork the dough to keep the pastry tender and flaky.
• Using a preheated baking sheet helps prevent a soggy base and promotes even cooking.
• Gruyère cheese adds a creamy and slightly nutty flavor; you can substitute with other cheeses like Emmental or Comté if desired.
• This tart is best served warm but can be enjoyed at room temperature.

• Prep Time: 25 minutes
• Cook Time: 30 minutes
• Category: Tart
• Method: Baking
• Cuisine: French

Keywords: onion tart, caramelized onion tart, savory tart, French tart, Gruyère cheese tart, easy tart recipe, savory pastry