6 cups boiled pinto beans, cooked just until
    almost tender, with cooking water*
1 cup tomato pur?
3 tablespoons powdered red chiles
1 teaspoon cayenne (optional)

Preheat oven to 325 degrees F. Stir tomato pur? and powdered chiles into the beans and their cooking water, cover the casserole and bake for about 1 hour or until the liquid has thickened to a sauce.

* Prepare the beans as in the Frijoles de Olla recipe, cooking them just until almost tender because they will cook further in this recipe.