I am terrible at Vector3 and CFrame so bear with me.
Here's the code I have:
repeat
part.Rotation = Vector3.Z(0) + Vector3.Z(-1)
wait(0.1)
until
part.Rotation == Vector3.new(0,45,-180)
What can I replace this code with?
Any answers are greatly appreciated.

3 comments
If this is all you're doing, you could do a for loop.
I could do a for loop. that's no problem, but I don't know how to call on a specific axis.
Consider looking at BodyAngularVelocity