Place foil on a cookie sheet. Place fish on the foil and season to taste with salt and pepper.
Top with pesto, tomatoes and then cheese (in order).
Bake for 12-15 minutes or until fish flakes with fork.
*Note: I don't care for pesto except in this recipe. To prevent wasting the rest of the pesto in the jar, I make one recipe for dinner and freeze the ingredients to have another day. Just place each of the ingredients (except salt & pepper) in its own quart-size freezer bag, then place all in a gallon-size freezer bag along with directions and freeze. When ready to make, just thaw completely and follow the above directions to prepare.