Coarsely grate the courgette. Lightly whisk the eggs with the salt, then mix in the parmesan. Add the grated courgette, combine gently.
Heat a knob of batter or a spoonful of olive oil in a frying pan. Pour in the mixture, put a lid on and cook for 5 minutes over low heat.
Cut the tomatoes in half and put these on top of the frittata (the surface should be jelly-like). Cook for a further 5-8 minutes until the surface is set.
Turn on your grill in the oven. Put the pan under the grill for a couple or until it’s golden.
Slide the frittata onto a plate, cut it into wedges and serve immediately.
Alternatively, let it cool completely and cut it into bite-sized squares.