Peel shallots and garlic, dice finely and sweat in hot oil until translucent. Stir in the pesto and season the mixture with pepper and chili powder.
Wash the tomatoes, cut them into slices and spread them in a greased baking dish. Wash the fish fillets, pat dry, season with salt and place on the tomatoes. Brush with the onion pesto. Wash the basil, pluck the leaves off and sprinkle over them. Bake in the preheated oven at 200 ° C for about 25 minutes.