In a Dutch oven or large stock pot, heat oil over medium heat. Add onions, peppers, garlic, cumin, cayenne, and chili powder, and season with salt and pepper. Stir together and cook until soft, 3 to 4 minutes.
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Mix in beans, tomatoes, and corn. Bring mixture to a boil, then lower heat and simmer for 30 minutes, stirring occasionally. Taste and season with additional salt and pepper, if necessary. Served with desired toppings. Leftovers will keep in the fridge for about a week or in the freezer for a couple months.