Add more dairy. Heat slowly. GL!

Agreed with PPs, and OP -- you may want to keep the sauce and pasta separate (i.e. only make enough pasta for the original meal, then reheat the sauce and boil new pasta for the leftovers meal).

Definitely no microwave.

Reheat slowly on the stove, and stir the entire time. Then eat immediately, because the sauce is still likely to separate on the plate.

First, don't reheat in the microwave. Second, throw in a little bit of milk or cream when you reheat, just like you would on mac & cheese, it helps to recreate the sauce. Hope that helps.

that's the nature of cream based sauces; no way around it unfortunately

Does anyone have any good ideas about how to best reheat cream based sauces so they won't separate? Whenever I stick, say, penne with vodka sauce in the microwave, I get pools of butter/fat/something and the sauce just totally breaks apart. There must be a better way to do this!