Do this one exercise to strengthen your buttocks and especially the side muscle in your butt.
You will also get stronger and more toned legs in addition to increased flexibility by doing it correctly in your hip flexors and in your hamstring.
Be aware that is an advanced exercise and you can lay on your side instead to make it easier.Have your back straight on the backside of the mat and your legs in an angle with your feet on the opposite side of the mat.
Do the exercise 1-2 times on each side, three times a week to increase your strength and tone your butt and legs!
All the best