Preheat the Oven and Prepare the Pan: Preheat your oven to 350°F (175°C). Spray a springform pan, round cake pan, or casserole dish with cooking spray.

Cook the Beef and Onion: In a large skillet, brown the ground beef over medium-high heat. Add the diced onion and cook until the onion is translucent and the beef is no longer pink. Drain excess fat. Stir in the taco seasoning mix according to package directions.

Layer the Casserole: Lay one tortilla in the bottom of the prepared baking dish. Spread 1/3 of the refried beans over the tortilla. Top with 1/3 of the seasoned meat mixture. Sprinkle with shredded cheddar cheese.

Build the Second Layer: Place another tortilla on top. Spread 1/2 of the prepared rice over the tortilla. Add 1/2 of the salsa, spreading it evenly. Sprinkle 1/2 of the drained corn over the salsa. Top with shredded cheddar cheese.

Build the Third Layer: Place another tortilla on top. Spread another 1/3 of the refried beans over the tortilla. Add another 1/3 of the seasoned meat mixture. Sprinkle with more shredded cheddar cheese.

Final Layer: Add the final tortilla on top. Spread the remaining refried beans over the tortilla. Top with the remaining seasoned meat. Add the rest of the corn and the remaining rice. Spread the remaining salsa over the top and sprinkle with the last portion of shredded cheddar cheese.

Bake the Casserole: Cover the baking dish with aluminum foil. Bake in the preheated oven for about 40 minutes. Remove the foil and bake for an additional 10-15 minutes, or until the cheese is melted and bubbly and the casserole is heated through.

Let it Set and Serve: Remove the casserole from the oven and let it sit for about 5 minutes before cutting. This helps the layers set and makes it easier to cut into neat pieces. Top with optional garnishes like sour cream, diced onion, and shredded lettuce if desired.