To make sure this exercise is targeting both your core and glutes, make sure you're not arching your back to lift up your foot.
Begin on your hands and knees, shoulders over wrists and hips over knees. Find a flat back and pull your core in toward your spine. This is your starting position.
Kick your right leg back while keeping the foot flexed and knee bent at a 90-degree angle. Try not to let your back arch as you kick the sole of your foot toward the ceiling. Activate and squeeze your glutes as you kick.
Lower your right leg with control to return to the starting position. Repeat with your left leg.