Fireball

A bright streak flashes from you to a point you choose within range and then blossoms with a low roar into a fiery explosion. Each creature in a 20-foot-radius Sphere centered on that point makes a Dexterity saving throw, taking 8d6 Fire damage on a failed save or half as much damage on a successful one.

Flammable objects in the area that aren't being worn or carried start burning.

Using a Higher-Level Spell Slot. The damage increases by 1d6 for each spell slot level above 3.