Scorching Spell (3.5e Feat)
From D&D Wiki
Scorching Spell [Metamagic]
Your fire magic is further bolstered, and burns your enemies to a crisp.
Prerequisite: Blistering Spell.
Benefit: A scorching spell deals an extra 3 points of fire damage for each die of damage the spell deals. This feat can only be applied to spells with the fire descriptor. For example, if a 9th level wizard with this feat casts a scorching fireball, the fireball deals 9d6+27 points of damage. A scorching spell uses up a spell slot two levels higher than the spell's actual level.