The information I found at D&D Beyond says this:
Using a resonant: You can use a Resonant when you cast a wizard spell with a spell slot and speak the true name of a target creature of the spell. Saying the name is part of casting the spell.
My question is, do cantrips count as spells in this context? My DM is not so sure as I think the spell needs to spend a spell space to be applicable, but I can't find any information to support this claim. Please pause and thank you in advance.