Notes: For ploenta rounds, buy two tubes (about 2 in. diameter; 2 lb. total) prepared polenta; cut into 3/8-inch-thick slices, discarding ends. It's worth spending a little extra for high-quality parmesan cheese (preferably Parmigiano reggiano) for this dish; grate just before using. You can prepare the roasted tomatoes for the pizzas up to 1 day ahead; when cool, cover and chill.
12 Roma tomatoes (about 3 oz. each)
About 1/4 cup purchased or homemade pesto
24 rounds (each about 2 in. wide and 3/8 in. thick) purchased cooked polenta (see notes)
1 cup grated parmesan cheese (about 3 oz.; see notes)
How to Make It
Rinse tomatoes, cut in half lengthwise, and place cut side up in an oiled 10- by 15-inch pan. Sprinkle lightly with pepper. Spread about 1/2 teaspoon pesto onto cut side of each tomato half.
Bake tomatoes in a 350° regular or convection oven until browned on top and slightly shriveled, 1 1/2 to 2 hours (if pan juices begin to scorch, add a few tablespoons water to pan). Let tomatoes cool about 10 minutes.
Place polenta rounds slightly apart on an oiled 12- by 17-inch baking sheet. Sprinkle 1/2 cup parmesan cheese evenly over rounds. Set a tomato half, pesto side up, on each and sprinkle remaining 1/2 cup cheese on top.
Bake polenta pizzas in a 450° regular or convection oven until cheese is melted and beginning to brown, 10 to 13 minutes. Let cool 2 to 3 minutes, then transfer with a spatula to a platter.