Source: Ruth White
There are many variations on the theme:
You can replace some of the pumpkin with a carrot, add a potato, use a dash of nutmeg or cinnamon instead of the cumin, leave out the tomato paste.
You can make a similar soup with sweet potato, seasoned with nutmeg or entirely of carrot, with the grated rind and the juice of an orange along with water or stock. Parsnip recipes often get sprinkled with bacon bits when you are serving. I've never tried a turnip soup - so feel free!
Potato soup usually has a chopped leek sweated in along with the onion, and my have cream stirred in just before serving, and a sprinkle of chopped chives or parsley.