Preheat the oven to 220°C/fan oven 200°C/Gas Mark 7.
Heat the olive oil in a frying pan and gently fry the onions until soft and beginning to brown about 5-6 minutes. Leave until cool.
Roll out the puff pastry on a lightly floured surface. Cut into a circle measuring about 30cm (12 inches) in diameter. Lift onto a lightly greased baking sheet.
Sprinkle the onions and cheese evenly over the surface of the pastry to within 2.5cm (1 inch) of the edge. Season with black pepper.
Bake for 20-25 minutes until the pastry is cooked and golden. Cool for a few moments and serve scattered with basil leaves.
Spread a thin layer of sun-dried or regular tomato puree over the pastry before adding the cheese and onions, if you like.
Use a pastry cutter to make smaller versions of this tart for a delicious starter or canapés.
Our thanks to Pilgrims Choice for providing this recipe.
For more delicious veggie recipe ideas, see our selection of vegetarian recipes.