Preheat oven to broil/ grill settings on high. Arrange oven shelf to middle of your oven. Combine the 2T oil, garlic and 4 tsp of the seasoning together in a small bowl. Brush the bottom of each mushroom with the garlic oil mix and place each mushroom, oil side down on a lightly greased baking sheet. Put a little of sauteed onions in the mushroom. S&P. Put 2T (eyeball it) of pizza sauce over the onion, 1/4C of mozzarella cheese on top of the sauce and pepperoni and tomato on top of cheese.