Concentrated Fireball

You create a small ball of fire on your hand. As an action on a different turn you can smash the ball against a creature or surface, making the ball blossom into a fiery explosion. Each creature in a 10-foot-radius Sphere centered on that point makes a Constitution saving throw, taking 8d8 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 1d8 for each spell slot level above 3.