Pre-heat the oven to 400 degrees, and position the cooking rack in the middle. Spread about half the sauce on the polenta crust and bake uncovered for 15 minutes. (This is a good time to cook the topping vegetables).
Remove the crust from the oven and spoon the cooked pizza toppings evenly over the top, finishing with the tomatoes. Bake uncovered for 15 minutes.
Serve after a minute of cooling. If you like, grate a few walnuts on top (using a rotary cheese grater); this makes a nice garnish in place of cheese. Cooked polenta crust is softer than wheat flour crusts, so this pizza is best eaten with a fork.