I used a 4" Portobello mushroom cap, snapping off the stem and using a spoon to scrape out the dark gills. Then a little squeeze of lemon juice on the prepared underside, and spread some nut butter right over that. I had raw tahini on hand, so that's what I used. Then a few thin slices of ripe tomato, sprinkled with chopped onion, and diced marinated Portobello mushroom "steaks" I also had in the fridge. A few fresh basil leaves, tightly rolled length-wise then sliced thinly for a chiffonade, and finally a sprinkle of nutritional yeast.
Hallellujah, pizza is back on the menu!