Crushing Haymaker

Your fist reverberates with destructive energy, and woe betide whatever it strikes. As part of casting the spell, make a melee spell attack against a creature or object within 5 feet. If you hit, the target of your attack takes 7d6 thunder damage, and must make a Constitution saving throw or be knocked prone and stunned until the end of its next turn. This spell's damage is doubled against objects and structures.