Step 1

Preheat an oven to 350 degrees F (175 degrees C).

Step 2

Fill a large pot with lightly salted water and bring to a rolling boil over high heat. Once the water is boiling, stir in the rotini, and return to a boil. Cook uncovered, stirring occasionally, until the pasta has cooked through, but is still firm to the bite, about 8 minutes. Drain well in a colander set in the sink.

Step 3

Place the cooked pasta into a large mixing bowl, and add the cream of mushroom soup, ketchup, green chiles, onion, and luncheon meat. Pour into a 9x13 inch baking dish, and evenly sprinkle with the Cheddar cheese.

Step 4

Bake in the preheated oven until the casserole is hot and the Cheddar cheese has melted, about 10 minutes.