Place spinach in a saucepan over low heat, or defrost in the microwave. Squeeze out excess juice from spinach.
Cut bacon rashers into strips and fry in a dry pan until crisp.
Meanwhile, butter flan dish.
Cut Swiss cheese slices diagonally and layer the base of the flan dish.
Reserve 5 slices of cheese for decoration.
Drain fat from bacon on paper towel.
Add butter and onion to bacon pan. Cook to soften, not brown.
Return bacon to the pan and add spinach, beaten eggs, cream and parmesan cheese. Season with salt and pepper. Mix ingrediants together and pour into dish.
Arrange remaining Swiss cheese slices and tomato slices on top. Bake for 20-30mins.
