1. Preheat the oven to 350 degrees.
2. Heat the olive oil (or water) in a large frying pan over medium-high heat.
3. Add the onion, bell pepper, and garlic and cook until softened, 5 to 7 minutes.
4. Remove from the heat and stir in the tomato sauce, black and pinto or mixed beans, corn, chili powder, cumin, salt and cayenne.
5. Pour mixture into an 8 X 8-inch glass baking dish.
6. Boil the water.
7. Add the cornmeal, lemon juice, mustard, and sea salt in a large saucepan, and stir until mixed.
8. Bring to a boil over medium-high heat, then immediately reduce the heat to low and simmer, stirring often, until thickened, 3 to 5 minutes.
9. Spread the cooked cornmeal over the bean mixture.
10. Bake for 30 minutes.
11. Cool for 10 minutes before serving.