Preheat oven to 350° F.

If using dried beans, rinse and sort. Cover with water and cook using your favorite method (see note). Alternately, drain and rinse canned beans; set aside.

Bring water to a boil in a heavy-duty sauce pan and season with salt. Pour polenta in a steady stream, stirring constantly to avoid lumps. Turn down the heat to medium and cook, stirring frequently, until smooth. You should barely see individual grains of cornmeal.

Spread half the cooked polenta into a large ceramic baking dish. Sprinkle with half the cheese, then the cooked beans. Sprinkle remaining cheese over beans, then pour salsa over. Spread remaining polenta over the top.

Bake for 15 to 20 minutes, until cheese is melted and bubbling.

Special notes:

I prefer to cook my beans using the quick-soak method: Bring rinsed beans to a boil, cover and turn off the heat. Let soak for 1 hour. Drain and rinse again. Cover beans with plenty of fresh water, and bring to a boil. Reduce heat and cook over medium heat for about 45 minutes, until done.