Thunder Punch

You charge your hand (or similar appendage) with thunder power. Make a melee spell attack against the target. On a hit, the target takes 3d8 thunder damage, and is knocked 10 feet away from you.

At Higher Levels. When you cast this spell using a spell slot of 3rd level or higher, the damage increases by 1d8 for each slot level above 2nd.

Source: Kibble's Generic Elemental Spells