Bring a large pot of salted water to a boil. Add the broccoli rabe and cook until crisp-tender, about 3 minutes. Drain. Meanwhile, broil both lemon halves until lightly charred, about 5 minutes. Remove and cool. Heat the oil and butter in a large skillet over medium heat. Add the garlic and cook about 2 minutes. Squeeze 1 lemon half into the skillet. Add the broccoli rabe, olives, salt, and pepper and heat through, about 2 minutes. Serve, using the other lemon half, cut into wedges, for garnish.