Preheat the oven to 350 degrees F (175 degrees C). Generously grease an 8-cup baking dish. Place baking dish on a cookie sheet.

Heat a large saucepan over medium-high heat. Cook and stir beef and onions until beef is browned and crumbly, 5 to 7 minutes. Drain off fat.

Drain liquid from canned tomatoes into a 4-cup measuring cup, adding water if needed, to make 2 1/2 cups of liquid. Add juice, tomatoes, macaroni, corn, bell pepper, garlic, soy sauce, chili powder, Italian seasoning, and pepper to the beef mixture; bring to a boil.

Pour 1/2 of the beef mixture into the prepared baking dish. Sprinkle with 1 cup of Mexican cheese, add remainder of beef mixture, and sprinkle with remaining cheese.

Bake, covered, in the preheated oven for 30 minutes. Remove cover and bake for another 15 minutes. Remove from the oven and let sit for 10 minutes before serving.