For the marinade, squeeze the lemon, finely dice the garlic and onion. Mix with the olive oil to a marinade, season with salt, pepper and basil. Add the salmon to the marinade and let it steep for at least 30 minutes.
Cut the tomatoes and mozzarella into slices. Put the salmon in a baking dish and drizzle a little with the marinade. Top it alternately with tomatoes and mozzarella so that the entire fish is covered. Put the pan in the oven and bake at 200 ° C for about 20 minutes.