Level
Cantrip
Casting Time
1 Action
Range/Area
Touch
Components
V, S
Duration
Instantaneous
School
Evocation
Attack/Save
Melee
Damage/Effect
Fire
Your palm glows white hot as you press it into a creature you try to touch. Make a melee spell attack against the target. On a hit, the target takes 2d6 fire damage, and it is vulnerable to fire until the end of your next turn.
The spell's damage increases by 1d6 when you reach 5th level (3d6), 11th level (4d6), and 17th level (5d6).
I definitely like the idea, but forcing damage vulnerability is a lot for just a cantrip. Consider making it a leveled spell- or at least getting rid of the damage. Also consider having it just downgrade fire resistance to no resistance rather than turning it into a vulnerability, and having no effect on creatures immune to fire.