Eldritch Firebomb

A dark, flaming ball of energy streaks toward a target within range and bursts in an explosion of eldritch fire. Make a ranged spell attack against the target. On a hit, the target takes 4d4 Fire damage and 2d4 Burning damage at the end of its next turn. On a miss, the bomb sears the target with fire for half as much of the initial damage only.

Using a Higher-Level Spell Slot. The damage (both initial and later) increases by 1d4 for each spell slot level above 2.