Dice the onion into 1/4-inch pieces, mince the garlic, and shred both the cheddar and Colby Jack cheeses (I always use freshly shredded cheese rather than pre-shredded because it melts much more smoothly and creates a creamier texture). Bring a large pot of salted water to a boil and add the macaroni, cooking it for 9 minutes until just al dente—it will finish cooking in the skillet, so don't overcook it here. While the pasta cooks, gather your spices (chili powder, paprika, and oregano) and measure them out.
Heat the olive oil in a large skillet over medium-high heat. Add the ground beef and diced onion, cooking and breaking up the meat for about 5 minutes until the beef is browned and the onion is softened. Add the minced garlic and cook for 30 seconds until fragrant. Reduce heat to medium, then sprinkle in the chili powder, paprika, and oregano, stirring constantly for 2-3 minutes to toast the spices and develop deeper flavors—this creates the foundation of the dish's taste.
While the spices are toasting, drain the cooked macaroni and set it aside. In a small bowl or measuring cup, combine the cream of mushroom soup, tomato sauce, mustard, and Worcestershire sauce, stirring until smooth. Pour this sauce mixture into the skillet with the cooked beef and aromatics, stirring well to combine and coat the beef evenly with the sauce.
Add the drained cooked macaroni to the skillet and stir thoroughly to coat it evenly with the sauce. Fold in the corn and the freshly shredded cheddar cheese, mixing gently but completely so all ingredients are well distributed throughout the dish. This step comes last because the cheddar needs minimal cooking time to prevent it from becoming grainy.
Top the casserole evenly with the shredded Colby Jack cheese, spreading it to cover the surface. Cover the skillet with a lid or aluminum foil and reduce the heat to low, cooking for 5 minutes until the top cheese is melted and creamy. I like to give it a gentle stir before serving so the melted Colby Jack distributes throughout the dish and creates an extra creamy bite.