Preheat the oven to 350°F (175°C) and spray a 9x13-inch baking dish with cooking spray.
In a large skillet over medium-high heat, brown the ground beef until no longer pink, breaking it up as it cooks.
Add the finely chopped onion and diced red bell pepper to the skillet and cook about 3 minutes until softened; drain any excess grease.
Stir in 1–2 tablespoons taco seasoning, the Rotel diced tomatoes, drained black beans, drained corn, and 1/2 cup salsa.
Add the softened cream cheese to the skillet and stir until melted and the mixture is well combined, then remove from heat.
In the prepared 9x13 dish, arrange 5 corn tortillas (they may overlap) in a single layer.
Sprinkle about 1/2 cup of shredded cheese over the tortillas, then spread half of the beef and bean mixture on top.
Place the remaining 5 tortillas over the first layer, then add the rest of the beef mixture evenly across them.
Top with the remaining shredded cheese, cover loosely with foil if desired, and bake for 25–30 minutes until the casserole is hot and bubbly.
Remove from oven and let rest a few minutes before slicing and serving with any desired toppings.