The Ultimate Makeover: Caramelized Onion Tart Recipe

Introduction

This onion tart is a delightful blend of sweet caramelised onions and a creamy, tangy filling nestled in a crisp, buttery base. Perfect for a light lunch or a stylish starter, it combines simple ingredients to create a rich, comforting dish.

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 only occasionally to allow them to caramelise and become sticky.
2. Step 2: While the onions cook, preheat the oven to 190°C (170°C fan)/gas mark 5 and place a baking sheet inside to heat.
3. Step 3: In a bowl, combine the self-raising flour, cold butter, and a pinch of salt. Rub the butter into the flour with your fingers until the mixture looks like rough crumbs.
4. Step 4: Mix the natural yogurt and semi-skimmed milk together. Pour this into the flour mixture and briefly combine with a knife until the dough just comes together. Avoid overworking it. Form the dough into a ball.
5. Step 5: Roll the dough out thinly on a lightly floured surface. Line a 23cm round, fluted, loose-based flan tin with the dough, pressing it gently into the fluted edges. Dust fingers with flour if the dough is sticky.
6. Step 6: In a medium bowl, beat the eggs. Stir in the crème fraîche, thyme leaves, Dijon mustard, and season with salt and pepper.
7. Step 7: Spoon and spread half of the caramelised onions evenly over the pastry base. Season lightly with pepper and sprinkle half of the Gruyère cheese on top.
8. Step 8: Pour the egg and crème fraîche mixture over the onions and cheese. Then scatter the remaining onions and cheese evenly on top.
9. Step 9: Place the tin onto the hot baking sheet in the oven and bake for 25-30 minutes until the filling is set and the base is cooked through.
10. Step 10: Remove from the oven and let the tart cool for about 10 minutes. Carefully remove it from the tin and serve warm for best flavor and texture.

Tips & Variations

• Use a mix of cheeses such as Gruyère and cheddar for a richer flavor.
• If you prefer a sweeter note, add a teaspoon of honey while caramelising the onions.
• For a gluten-free version, substitute the self-raising flour with a gluten-free flour blend.
• Fresh thyme can be replaced with rosemary or sage for a different herbal twist.

Storage

Store any leftover tart in an airtight container in the refrigerator for up to 2 days. Reheat slices gently in a low oven or microwave until warmed through. This tart is best enjoyed fresh and warm, but can be served at room temperature as well.

How to Serve

Serve this delicious recipe with your favorite sides.

FAQs

Can I use yellow onions instead of red onions?

Yes, yellow onions will work well. They tend to be sweeter when caramelised, which complements the creamy filling nicely.

Is it possible to make the tart in advance?

Absolutely. You can prepare the tart and bake it earlier in the day. Reheat gently before serving to enjoy it warm and fresh.

The Ultimate Makeover: Caramelized Onion Tart Recipe

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★★★★★

4.9 from 167 reviews

• Author: Jake
• Total Time: 55 minutes
• Yield: 6 servings 1x
• Diet: Vegetarian

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Description

This delicious onion tart recipe features sweet caramelised red onions nestled in a creamy, cheesy custard filling on a crisp, homemade yogurt and milk-based pastry crust. Perfect for a light lunch or elegant appetizer, the tart combines rich Gruyère cheese with fragrant thyme and Dijon mustard for a flavorful and comforting dish that’s sure to impress.

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Ingredients

Scale 1x2x3x

Onion Filling

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

Pastry Base

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

Custard Filling

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

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Instructions

1. Caramelise the onions: Slice the halved onions into 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 cook for about 20 minutes, stirring occasionally to allow them to caramelise evenly and become sticky and well browned underneath.
2. Prepare the pastry dough: While the onions cook, preheat your 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, salt, and cold butter. Rub together with your fingers until the mixture resembles coarse crumbs. Mix the natural yogurt and semi-skimmed milk together, then pour into the flour mixture. Using a knife, briefly work it all together until the dough just comes together. Be careful not to overwork. Gently press into a ball.
3. Roll and line the tart tin: Lightly flour a surface and roll the dough out thinly. 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. Place the lined tin on the hot baking sheet in the oven to warm slightly while you prepare the filling.
4. Make the custard and assemble the tart: In a medium bowl, beat the eggs, then stir in the crème fraîche, thyme leaves, Dijon mustard, salt, and pepper to taste. Spoon half of the caramelised onions evenly over the pastry base and scatter over half of the grated Gruyère. Pour the egg and crème fraîche mixture over the onions and cheese evenly. Top with the remaining onions and Gruyère cheese.
5. Bake the tart: Place the tart tin on the preheated baking sheet and bake in the oven for 25-30 minutes until the pastry base is cooked through and the filling is set and golden on top.
6. Cool and serve: Remove the tart from the oven and let it cool in the tin for about 10 minutes. Carefully remove the tart from the tin and serve warm for best flavor and texture.

Notes

• Ensure onions caramelise slowly over medium heat to develop maximum sweetness and flavor.
• Do not overwork the dough to keep the pastry light and flaky.
• Use a loose-based flan tin for easy removal of the tart after baking.
• Letting the tart cool slightly helps the filling to set and makes it easier to slice.
• This tart is delicious served warm with a side salad for a complete meal.

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

Keywords: onion tart, caramelised onion tart, savory tart, vegetarian tart, Gruyère cheese tart, homemade pastry, French tart recipe