lemon butter vs butter

lemon butter and butter both are nouns.

Word	Noun	Adjective	Verb	Adverb
lemon butter	Yes	No	No	No
butter	Yes	No	Yes	No

As nouns, butter is a hypernym of lemon butter; that is, butter is a word with a broader meaning than lemon butter:

lemon butter: clarified butter browned slowly and seasoned with lemon juice and parsley
butter: an edible emulsion of fat globules made by churning milk or cream; for cooking and table use

lemon butter (noun)	butter (noun)
clarified butter browned slowly and seasoned with lemon juice and parsley	an edible emulsion of fat globules made by churning milk or cream; for cooking and table use
	a fighter who strikes the opponent with his head

lemon butter (verb)	butter (verb)
	spread butter on