hot cross bun vs cross bun

hot cross bun and cross bun both are nouns.

Word	Noun	Adjective	Verb	Adverb
hot cross bun	Yes	No	No	No
cross bun	Yes	No	No	No

As nouns, hot cross bun and cross bun are synonyms defined as:

hot cross bun and cross bun: moderately sweet raised roll containing spices and raisins and citron and decorated with a cross-shaped sugar glaze

hot cross bun (noun)	cross bun (noun)
moderately sweet raised roll containing spices and raisins and citron and decorated with a cross-shaped sugar glaze	moderately sweet raised roll containing spices and raisins and citron and decorated with a cross-shaped sugar glaze