Portobello Mushroom Cap Pizza Recipe | This easy pizza recipe combines your favorite margarita pizza ingredients, but uses a large mushroom cap as the base for an easy veggie crust! Start with a layer of your favorite pesto, then stuff the mushrooms with mozzarella cheese and fresh tomatoes. Baked in the oven and ready in under 30 minutes! Top with fresh basil and a drizzle of balsamic vinegar. An easy, healthy weeknight dinner that’s easy to customize! Vegetarian, Gluten-Free.