The info I found on D&D Beyond says this:
Using a Resonant: You can use one Resonant when you cast a wizard spell with a spell slot and speak the true name of one creature targeted by the spell. Speaking the name is part of casting the spell.
My question is, would cantrips count as spells in this context? My DM isn't so sure, being of the opinion that the spell needs to expend a spell slot to be applicable, but I can't find any info to support this claim.