Place mushroom caps top-side down on a wire rack over a rimmed baking tray. This will prevent the mushrooms from getting soggy as liquid is released while baking. Sprinkle each mushroom cap with a dash of salt.
Spread 1 tbsp marinara over each mushroom cap and top with a tomato slice, then a mozzarella slice.
Drizzle olive oil over pizzas, then add minced garlic.
Bake for 15-18 minutes until cheese is melted.
Remove from oven and top with basil leaves for garnish. Enjoy!