Blue-Flame Blade

You brandish the weapon used in the spell’s casting in blue flames and make a melee attack with it against one creature within 5 feet of you. On a hit, the target suffers the weapon attack, and takes fire damage equal to your spellcasting ability modifier.

This spell’s damage increases when you reach certain levels. At 5th level, the melee attack deals an extra 2d8 + your spellcasting ability modifier fire damage to the target on a hit. Both damage rolls increase by 2d8 at 11th level (4d8) and 17th level (6d8).