Blistering Spell (3.5e Feat)
From D&D Wiki
Blistering Spell [Metamagic]
Your fire spells sear the flesh from your enemies' bones, leaving them wracked with pain.
Benefit: This metamagic feat can be applied only to a spell that has the fire descriptor. A blistering spell deals an extra 2 points of fire damage per level of the spell. In addition to the spell's normal effect, any creature that fails its save against a blistering spell takes a -2 penalty on attack rolls and checks until the beginning of your next turn. A blistering spell uses up a spell slot one level higher than the spell's actual level.