Preheat oven to 400F (205c). Set oven rack in center of oven.
Into an oven safe 10" (25cm) skillet (I use cast iron), add the oil and heat until shimmering. Add the onions and bell peppers. Cook on medium-low for about 9-10 minutes, or until softened, stirring occassionally. Charring is good.
To the skillet, stir in the jalapeños and garlic. Sprinkle in the chili powder, ground black pepper, salt and masa harina. Stir to coat vegetables, about one minute. Stir in the tomato paste, tomatoes, broth, oregano, and beans. Warm to a simmer, then remove from heat. Taste for salt adjustment, reseason if needed.
Sprinkle the cheese over the top if using (or 1/2 the amount for those who may not want cheese), then arrange the tater tots on top of the cheese (or over the chili) in a circular pattern. Bake in a 400F preheated oven for 30 minutes, until tater tots are golden and crisp and the chilly is bubbling underneath.
Serve with avocado, jalapeños, cilantro, green onions, and/or sour cream. Store in a lidded container in the refrigerator for up to three days. Freeze for up to two weeks.