Preheat the oven to 350 F. Clean the mushrooms with a damp towel or mushroom brush. Lightly spray both sides of cleaned mushrooms with Pam. Place mushrooms gill side up on a baking sheet and bake for 6 minutes to soften.

Remove portabellas from the oven and spoon 1 or 2 tablespoons of tomato sauce on top gill side of each. Place a basil leaf in each center, sprinkle with 2 tablespoons of cheese and some chopped tomato. Return to the oven and bake for 7 more minutes. Serve immediately.