To prepare chili: Heat oil in a Dutch oven over medium heat. Add onion and cook until beginning to soften, about 4 minutes. Add bell pepper and garlic and cook for 1 minute. Add beef and cook, breaking it up with a wooden spoon, until browned, 4 to 5 minutes. Stir in beans, tomatoes and their juice, chili powder, cumin, paprika and cayenne (if using). Bring to a boil; reduce heat to maintain a simmer, cover and cook until slightly thickened, about 20 minutes.
Preheat oven to 350°F. Coat a 9-by-13-inch (or similar 3-quart) baking dish with cooking spray.
To prepare cornbread: Whisk cornmeal, flour, sugar, baking powder, baking soda and salt in a large bowl. Whisk egg, milk and oil in a medium bowl. Add the wet ingredients to the dry ingredients along with cilantro and stir until just combined. Transfer the chili to the prepared baking dish and sprinkle with cheese. Spread the cornbread batter evenly over the chili.
Bake the casserole until the top springs back when touched lightly, 20 to 25 minutes. Let stand for 10 minutes before serving.