Brimstone Blast

You hurl a beam of crackling fire. Make a ranged spell attack against one creature or object in range. On a hit, the target takes 1d10 Fire damage. On hit the target makes a Dex saving and on a failure is set on fire. While on fire the creature takes 1d10 fire damage at the start of it's turn until it uses an action to put itself out or another creature uses an action to put them out. 

Cantrip Upgrade. The spell creates two beams at level 5, three beams at level 11, and four beams at level 17. You can direct the beams at the same target or at different ones. Make a separate attack roll for each beam.