Preheat the oven to 180°C, Gas Mark 6.
Wash the tomatoes and dry with a cloth.
Peel the onions, removing the green part of the stalk and then cut into two.
Melt 30g butter in a frying pan, add the onions and the sugar, grind on some pepper and leave to caramelise gently over a medium heat, stirring constantly. Grease a nonstick cake tin and arrange the slightly caramelised tomatoes and onions in it.
In a mixing bowl, beat the eggs, season with salt and pepper and then add the corn flour, milk and cream, beating constantly. Pour the mixture over the tomatoes and onions and bake in the bottom of the oven for 20 minutes.
Serve hot, straight from the oven.
Why not serve accompanied by fish or poultry. Try warm or cold alongside a salad.