You can by RAW
Cantrips are level 0 spells:
A cantrip's spell level is 0.
You can cast a spell at a higher level:
When a spellcaster casts a spell using a slot that is of a higher level than the spell, the spell assumes the higher level for that casting. For instance, if Umara casts magic missile using one of her 2nd-level slots, that magic missile is 2nd level.
This mechanic is called "Casting a Spell at a Higher Level". There is no mention of a requirement for a spell to be using a spell slot. The only requirements is for it to be a "spell" and for it to have a "spell level". The mechanic says that you can use slots of higher level than the spell (eg, 3 is higher than 0) to increase the level of the spell.
Why do it?
Consider this example:
If Umara casts light using one of her 3rd-level slots, that light is 3rd level
This would be useful for creating light in Darkness: "If any of this spell's area overlaps with an area of light created by a spell of 2nd level or lower, the spell that created the light is dispelled."