closeup on slice of onion tart on a board

Onion Tart

Sweet caramelised onions in a pastry case with a savoury custard. Ideal for picnics or lunch.
Course lunch
Cuisine French
Skill Level Moderate
Prep Time 30 minutes
Cook Time 1 hour
Chilling Time 30 minutes
Total Time 2 hours
Servings 4 -6 people
Calories 519kcal
Author Jacqueline Bellefontaine



  • 200 g plain flour
  • 100 g butter
  • cold water to mix


  • 25 butter
  • 2 tbsp  olive oil
  • 900 onion halved and thinly sliced
  • 2 large eggs
  • 150 ml single cream
  • salt and freshly ground black pepper
  • pinch grated nutmeg
  • 75 g gruyere cheese grated (or a vegetarian cheese)


  • Place the flour in a mixing bowl. Cut the butter into cubes and add to the flour.
  • Using your fingers, rub in the butter until the mixture resembles fine bread crumbs.
  • Add enough water to mix to a firm dough. Cover your pastry and allow to rest for at least 15 minutes before rolling out and using as required.
  • Preheat the oven to 200℃ (180℃ fan)/400°F/gas mark 6.
  • Roll the pastry and use to line a deep 20cm flan tin. Prick the base of the flan and chill for 15 minutes.
  • Line the case with baking parchment and baking beans and bake for 10 minutes. Remove parchment and baking beans and bake for about 5 minutes until the pastry case is pale golden.
  • Reduce the oven temperature to 180℃ (160℃ fan)/400°F/gas mark 4.
  • Meanwhile, melt the butter with the oil and cook the onions slowly for about 15 minutes until the onions are soft and just beginning to caramelise and brown.
  • Beat the eggs and cream together with salt, pepper and a pinch of nutmeg.
  • Spread the onions in an even layer in the pastry case and sprinkle the cheese on top.
  • Carefully pour in the egg mix bake the tart on the baking sheet for about 40 minutes until the filling is firm and golden, and the pastry crisp. Serve warm or cold.


Serve Hot or cold.

Nutrition information is approximate and is meant as a guideline only. (It does not include seasoning with salt and pepper.) 


Calories: 519kcal | Carbohydrates: 40g | Protein: 11g | Fat: 35g | Saturated Fat: 19g | Cholesterol: 140mg | Sodium: 226mg | Potassium: 309mg | Fiber: 3g | Sugar: 6g | Vitamin A: 19.4% | Vitamin C: 13.6% | Calcium: 19.5% | Iron: 11.8%