Add butter to a skillet and melt over medium heat.
Add in the onion and allow to saute for about 2 minutes.
Add in the asparagus and saute an additional 3 minutes.
Add in the shrimp and cook 4 minutes.
Sprinkle desired amount of Cajun, salt and pepper over shrimp and veggies.
Pour in the Rotel and Half & Half.
Simmer mixture over low heat for about 5 minutes.
Remove from heat and pour over pasta.
Toss to coat thoroughly and sprinkle Parmesan cheese on top