How to Make It
Stir together feta, lemon zest, crushed red pepper, and 1 tablespoon oil in a small bowl. Set aside to marinate.
Whisk together yogurt, lemon juice, garlic, salt, black pepper, and remaining 2 tablespoons oil in a large bowl.
Cook penne according to package directions. Reserve ½ cup cooking water and drain. Add hot penne to yogurt mixture. Toss, adding cooking water 2 tablespoons at a time until desired consistency is reached. Gently stir in arugula. Top with marinated feta and chives.