onion salt vs seasoning

onion salt and seasoning both are nouns.

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

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

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

onion salt (noun)	seasoning (noun)
ground dried onion and salt	the act of adding a seasoning to food
	something added to food primarily for the savor it imparts