onion salt vs flavouring

onion salt and flavouring both are nouns.

Word	Noun	Adjective	Verb	Adverb
onion salt	Yes	No	No	No
flavouring	Yes	No	No	No

As nouns, flavouring is a hypernym of onion salt; that is, flavouring is a word with a broader meaning than onion salt:

Other hypernyms of onion salt include flavorer, flavoring, flavourer, seasoner, seasoning.

onion salt (noun)	flavouring (noun)
ground dried onion and salt	something added to food primarily for the savor it imparts