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.
Ingredients
Scale
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
Instructions
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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
