Choose a new cookbook worth up to £28 when you subscribe to our magazine.
Heat oven to 220C/200C fan/gas 7. Heat the butter in a frying pan until sizzling, then add the bacon and cook for 6 mins until just starting to crisp. Add the onions and sweat for 10 mins until soft, sticky and golden. Pour in the cream, take off the heat and leave to cool a little.
Meanwhile, roll the pastry out on a lightly floured surface to a rectangle a little larger than this magazine and transfer to a baking tray. Roll the edges up and press down to create a raised border.
Tip the creamy onions into a bowl. Mix in the grated cheese and most of the beaten egg. Spread the mixture over the pastry, then scatter over the tomatoes and crumbled cheese. Brush the borders with the remaining beaten egg, then bake for 20 mins until golden. Leave to cool, then cut into squares. Enjoy warm with salad or cold on a picnic.