Cook pasta according to package directions. Meanwhile, cook the mince and onion over medium heat in a large saute pan until the meat is cooked through.
Drain both the mince and the pasta then add the pasta to the mince mixture.
Stir in the tomatoes, relish, mustard, ketchup, steak seasoning and seasoned salt. Bring to a boil, then reduce the heat and simmer, uncovered, for 5 minutes.
Sprinkle with cheese. Remove from the heat; cover and let stand until cheese is melted. Garnish with spring onions if desired.