Burning blade

Evocation cantrip
Casting Time: 1 action
Range: Self (5-foot radius)
Components: V, M (a melee weapon)
Duration: 1 round
As part of the action used to cast this spell, you must
make a melee attack with a weapon against one
creature within the spell’s range, otherwise the spell
fails. On a hit, the target suffers the weapon attack’s
normal effects, except that any damage dealt by
the attack is fire damage instead of its normal type.
Additionally, embers whirl in the target’s space. Until
the start of your next turn, when a creature enters
the space for the first time or ends its turn there, you
can use your reaction to deal 1d6 fire damage to the
creature, ending the spell.
This spell’s damage increases when you reach
certain levels. At 5th level, the melee attack deals an
additional 1d6 fire damage to the target on a hit and
the secondary damage deals an additional 1d6 fire
damage to its target. Both damage rolls increase by
one die at 11th level (2d6 and 3d6) and 17th level
(3d6 and 4d6).