Soak the tomatoes in a bowl for 15 minutes with just enough hot water to cover them.
Remove from the water (keep the water) pat dry with kitchen paper and cut into fine strips.
Fry the onion in the oil until soft and brown, then add the tomato strips and thyme.
Cook for a further 2 minutes, stirring constantly.
Season to taste with black pepper.
Beat all 6 eggs into a bowl, stir in 3 tbsps of the tomato water and all the parmesan.
Raise the heat under the pan, when the oil sizzles, add the egg mixture.
Mix quickly then stop stirring.
Turn the heat to low, cook until the base is golden and the top is puffed.
Using a large plate as a lid, turn the pan over, the frittata will land on the plate, place the golden cooked side up and slide the frittata back in the pan until the other side is cooked
Cut into bite sized wedges and offer hot or cold.