Preheat oven to 175 degrees C. Grease a baking tray with cooking spray.
Beat egg and lemon juice together in a bowl.
Mix breadcrumbs, Romano cheese and adobo seasoning together on a plate. Dredge chicken breasts in the egg mixture, coat with breadcrumb mixture, and place on the prepared tray.
Bake in the preheated oven until no longer pink in the centre and the juices run clear, about 20 minutes. Flip chicken breasts over and spoon tomatoes and mozzarella cheese on top. Continue baking until cheese is melted, about 5 minutes more.