1. Preheat the oven to 200ºC/ Fan 180ºC/ Gas 6. Roll out the pastry on a lightly floured work surface to a circle shape, about 3mm-4mm thick. Use the pastry to line a 20cm deep loose-bottomed flan tin. Line with foil and uncooked rice or dry beans and bake for 12-15 minutes until lightly golden. Remove foil.
2. While the case is cooking, cook the peas in a pan of boiling water for 2-3 minutes until just tender. Drain. Heat the oil in a frying pan and cook the salad onions and courgette for 5 minutes until softened and golden. Add the peas and stir together.
3. Beat the ricotta with the eggs, milk and seasoning. Stir in the peas and onion mixture and use to fill the pastry case. Arrange the halved tomatoes around the edge. Scatter with Parmigiano and bake for 30-35 minutes until golden and puffy.