Thaw the creamed spinach, mix with the crème fraîche and season with salt and pepper.
Place the frozen fish fingers on a baking sheet lined with baking paper and bake at 220 degrees (convection 200 degrees) for about 15 minutes.
Then layer the fish fingers alternately with spinach and lasagne sheets in a baking dish. Wash and slice the tomatoes. Top the lasagna with it and sprinkle with cheese, bake for another 20 minutes and serve.