This is a good recipe for people who are watching their carbohydrate intake. Portobellos are meaty and hearty and make an unusual and tasty base for a pizza.
Variations:
Briefly rinse the mushrooms under cold running water to remove any dirt and grit, and pat them dry. Trim and discard the ends of the stems. Carefully cut the remaining stems out of the mushrooms and set them aside.
Sprinkle the ridged underside of each mushroom cap with oregano, and salt and pepper to taste.
Chop the reserved mushroom stems. In a small bowl, toss the stems with the green peppers, onions, and tomato. Sprinkle this mixture over the underside of the mushroom caps. Top them with the goat cheese and parmesan cheese.
Carefully spray the preheated baking sheet with vegetable oil spray. Place the mushroom caps cheese side up on the baking sheet and bake them for 8 to 10 minutes, or until the cheese has melted and is bubbly.