1. Cut the red onion into slices and place in a mixing bowl with the olive oil, salt and pepper.
2. Cut the puff pastry into 3 even-sized rectangular pieces, carve a square pattern, 1cm from the edge, on the surface of the dough, make sure not to cut through the dough. This will create a puffy crust and a flatter centre.
3. Brush the pastry twice with the beaten egg.
4. Keeping inside your square, spread the onion out. Cut your left over cheese into slices and spread out evenly on top of the onion.
5. Bake the puff pastry in the oven at 400°C for 15 minutes (convection oven).
6. While in the oven cut cherry tomato into quarters and mix with olive oil, parsley and season with salt and pepper.
7. When the puff pastry is cooked, divide the tomatoes out on top and serve right away on a serving tray or wooden board.
Adjust the flavour by using your favourite herbs