Preheat the oven to 200°C.
Grease the tart tin.
Mix the flour, cornmeal, Parmesan and a pinch of salt.
Rub in the butter and knead to a dough, adding 1-2 tbsp cold water if necessary.
Wrap in foil or clingfilm and chill for 30 minutes.
Roll the pastry out approximately 5 mm thick on a floured work surface and use to line the greased tin, forming a rim at the edge.
Prick several times with a fork. Cut a circle of aluminium foil, lay on the pastry and weigh down with rice.
Bake in the preheated oven for 10 minutes.
Then remove the aluminium foil and rice and set aside.
Reduce the oven temperature to 180°. For the filling, bring to the boil a pan of salted water.
Add the sugar and corn and cook for 5 minutes, until soft.
Leave to cool slightly then scrape the kernels off the cobs.
Melt the butter in a frying pan and sweat the spring onions until translucent. Beat the eggs and egg yolks, add the cream and season with salt and pepper.
Spread the sweetcorn kernels, spring onions and dill on the base of the part-baked pastry case.
Pour the egg mixture over and bake in the oven for 30 minutes, until golden. 10 minutes before the end of the baking time put the tomatoes on top of the tart and return to the oven for the last 10 minutes.