These vegetable-based 'pizzas' have been a long-time favorite in our members' kitchens. For this version, we are making them with the Caprese-inspired toppings of sliced tomatoes and fresh mozzarella. Serve a simple white bean salad on the side.
Bell peppers - (If prepping right before cooking, get oven heating first.) Chop bell peppers. (Can be done up to 5 days ahead)
Make salad dressing - Whisk together Italian seasoning (portion for salad), mustard, vinegar, and olive oil (portion for salad). (Can be done up to 5 days ahead)
Portobello mushrooms - Remove stems. Using the side of a spoon, scrape out the inside gills (the dark ridge-y stuff). (Can be done up to 3 days ahead)
Brush mushrooms on both sides with olive oil (portion for mushrooms). Place mushrooms stem-side up (even though the stems are gone) on a sheet pan.
Bake mushrooms until nearly tender, 10 to 15 minutes (depending on the size of the mushrooms).
Remove mushrooms from the oven and drain / dry with paper towels if they have released a lot of moisture.
Season each mushroom with some salt and pepper and Italian seasoning (portion for mushrooms). Add a slice of tomato to each mushroom and top with basil and then cheese.
Return mushrooms to oven and continue cooking for an additional 10 to 15 minutes, until cheese is bubbly.