The Rond de Jambe exercise works your butt, hips, and legs. Do 2 sets of 12 reps on each side.
Play Away the Pounds! Rond de Jambe: Step up on the bench and slowly sweep your leg forward in a semi-circle. Step down, and that's one repetition. You're going to do 12 repetitions per leg. Really keep your hips nice and level to target those glutes.