Demon fireball

A dark streak flashes from your hand finger to a point you choose within range and then explodes with a load boom into an explosion of demonfire. Each creature in a 5-foot-radius sphere centered on that point must make a constitution saving throw. A target takes 2d6 fire damage on a failed save.

It will burn everything not worn or carried.

With a level 3 or more slot: It will do 1d6 more damage