Toast with flounder fillet

Wash the flounder fillet, dry, drizzle with lemon juice, salt, pepper and marinate. Cut the onions into rings, put out in a small amount of butter until transparent, add fish fillet to it and simmer together for a few minutes. Cut the bread into slices, fry lightly, put slices of fish on it, top the rings of stewed onions. Cut the tomatoes into circles, put the circles on toast, put slices of cheese on top. Bake in the oven until the cheese melts. Sprinkle over the parsley greens and serve.