First make the sauce. Melt the butter in a wide saucepan, Add the garlic and stir for about 30sec or so, then add the pumpkin, rosemary, lemon zestand nutmeg. Season.
Cover and Sweat over a gentle heat for about 15 mins, stirring occasionally until the pumpkin is very soft. Squash a little down into the butter but leave about two-thirds as it is. Taste and adjust the seasoning.
Meanwhile cook the pasta.
Tip the drained pasta into the pumpkin pan and gentle mix. Serve immediately.