This recipe is definitely not a traditional pizza recipe. Instead of using a traditional crust made from dough, these portobello mushroom pizzas use the vegetable instead! The great thing about these pizzas is that they can be topped with whatever your heart and appetite desire!
Remove the stem of each mushroom and place them on a parchment-lined baking sheet pan, smooth side down. Drizzle the mushrooms with olive oil and red wine vinegar. Roast in the preheated oven until the caps are beginning to brown, 10 minutes. Once partially roasted, remove the mushrooms from the oven. If they have juice pooling into the caps, remove the juice using a paper towel.
While the mushrooms are roasting, brown the sausage over medium heat. Dice up the removed stems from the mushrooms and add them to the sausage. Cook until the sausage is cooked through, 6-7 minutes. Once the sausage is cooked, remove it from the heat and set it aside.
In a small bowl, combine the tomato sauce, basil, oregano, garlic, red pepper flakes, and salt. Stir to combine. Top each mushroom with 1-2 tbsp of the sauce, meat, pepper, and onion. Tear pieces of cheese onto the small pizzas, leaving some open spaces to see the toppings as the cheese melts.
Place the pizzas in the oven until the cheese is melted and beginning to brown, 10 minutes. Once baked, remove the pizzas from the oven and serve.