Heat the oven to 350ºF.

Heat 1 tablespoon neutral oil in a large skillet over medium-high heat until shimmering. Add 1 finely chopped white onion and 1 diced medium red bell pepper and cook, stirring occasionally, until the onions are translucent and slightly softened, about 4 minutes.

Add 1 pound lean ground beef and cook, breaking it up into small pieces with a wooden spoon, until cooked through and browned, 6 to 8 minutes. Stir in 2 tablespoons tomato paste and 1 (1-ounce) packet taco seasoning. Cook until fragrant and the tomato paste is slightly darkened, about 2 minutes.

Stir in 2 cups frozen corn kernels and 1 drained (7-ounce) can diced green chiles, scraping up any browned bits from the bottom of the pan. Remove the pan from the heat.

Reserve 1 cup enchilada sauce from 2 (10-ounce) cans. Stir the remaining enchilada sauce into the beef mixture. Taste and season with kosher salt as needed.

Mix 8 ounces shredded Monterey Jack and 8 ounces shredded mild cheddar cheese together in a medium bowl.

Spread ½ cup of the reserved enchilada sauce in the bottom of a 9x13-inch baking dish. Arrange 6 of the corn tortillas in an even layer on top (they can overlap). Dollop and spread ½ of 1 (16-ounce) can refried beans (generous ¾ cup) evenly over the tortillas. Spread half of the beef mixture (about 3 cups) over the beans, then sprinkle with ⅓ of the cheeses (1 ⅓ cups). Repeat layering the tortillas, refried beans, beef mixture, and cheeses. Top with the remaining 6 tortillas. Spread the remaining ½ cup enchilada sauce over the tortillas, then sprinkle with the remaining cheese.

Place the baking dish on a rimmed baking sheet. Bake until the cheeses are melted and the filling is bubbling, 30 to 35 minutes. Let cool for 10 minutes before serving. Serve with desired toppings.