Remove brown gills from the undersides of portobello mushrooms using a spoon; discard gills. Place mushroom caps, undersides down, on a baking sheet coated with cooking spray. Broil for 5 minutes.
Turn mushroom caps over; sprinkle evenly with black pepper and salt. Top each cap with 2 tablespoons Basic Marinara and 1 tablespoon grated Parmesan cheese. Broil 3 minutes or until cheese melts.