Toss onion, lemon, and rosemary in a bowl. Season with salt and pepper.
Heat olive oil in skillet over medium high heat. Add chicken thighs, skin down, and cook for 7-8 minutes. Flip and cook for another 6-8 minutes.
Remove chicken from the skillet and place on a plate. Drain excess fat from the skilled. Add lemon, onion, and rosemary to skillet and cook until lemon caramelizes and browns. Add chickpeas and cook for 2-3 minutes. Add kale and return chicken to skillet and cook for 1-2 minutes until internal temperature reaches 165°F.