Warm cream: In a saucepan over medium-low heat, warm the heavy cream with ground mustard, garlic powder, onion powder, and a pinch of cayenne until hot but not boiling, 3-5 minutes, stirring.
Melt cheese: Reduce heat to low. Gradually stir in the shredded cheese until melted and smooth. Do not boil hard or the sauce can separate.
Toss: Add the cooked pasta and toss until coated. Taste and adjust cayenne. Serve hot.