Source: Xanathar’s Guide to Everything

School: Conjuration

Casting Time: 1 Action

Range: 60 Feet

Duration: Concentration, up to 1 minute

Components:  V, S

You create a bonfire on ground that you can see within range. Until the spell ends, the bonfire fills a 5-foot cube. Any creature in the bonfire’s space when you cast the spell must succeed on a Dexterity saving throw or take 1d8 fire damage. A creature must also make the saving throw when it enters the bonfire’s space for the first time on a turn or ends its turn there.

At Higher Levels. The spell’s damage increases by 1d8 when you reach 5th level (2d8), 11th level (3d8), and 17th level (4d8).