Thinly slice the aubergines, soak in salted water for at least 1 hour, then drain and pat dry.Lightly dredge the slices in the flour and fry in hot oil, a few at a time, on both sides until golden – about 2 minutes.
Remove with a slotted spoon,drain on kitchen paper:- cool completely. In a mixing bowl, whisk the eggs well, add the tomatoes (optional) and season with salt and pepper. Warm 1 tbsp of olive oil in a non-stick frying pan. When the oil is quite hot, pour in one third of the egg mixture, spread a layer of aubergines, pour over another third of egg mixture, layer the rest of the aubergines and pour the rest of the eggs on top. Reduce the heat, cook for 5 to 6 minutes and occassionally shake the pan.
Cover the pan with a plate and turn over the frittata. Slide the frittata back into the pan and cook the other side for a further 5 minutes.
Turn out on a platter and serve.