Clean the fish, remove the gills and rinse well. Make oblique incisions on it every one and a half centimeters, this is necessary in order for it to be better baked and soaked in salt and seasonings.
Put the fish in a deep pan, season with salt and pepper and pour olive oil on both sides. RUB it with your hands. If it doesn't fit completely, you can trim the tails.
Cut the onion into half rings, garlic straws, 1/3 lemon slices, put everything in a deep bowl, add cherry tomatoes, half a teaspoon of salt, 2 tablespoons of olive oil, chop black pepper. Mix well so that everything is covered with oil.
Add all the ingredients to the fish, squeeze the lemon juice on the fish, put in a preheated oven and bake for 20 minutes at 200 degrees. Heat in the oven turn on the top and bottom. Cover with foil is not necessary.