Prepare the mold: brush it with vegetable oil. Wash the fish fillet (I have tilapia), add salt and pepper, and put it on the bottom of the mold so that it is closed. Top with a generous sprinkle of onion, cut into quarter rings.
Cut the vegetables into small cubes, add salt and pepper, add a little vegetable oil, and mix.
Spread the vegetables on the fish, put it to bake in a preheated 180 degree oven for 20 minutes.