Place a rack in center of oven. Preheat oven to 425°F. Coat a shallow roasting pan with cooking spray.
Remove skin and excess fat from chicken; pat dry with a paper towel. Arrange in roasting pan.
In a bowl, combine yogurt, dressing mix and pepper. Pour mixture over chicken; mix to coat. Refrigerate for 20 minutes. Before baking, sprinkle chicken with pecans. Roast for 15 minutes. Reduce heat to 350°F and roast until a thermometer inserted into thickest part of meat but not touching bone reads 170°F, 35 to 40 minutes more.
Mix pesto, lemon juice, mayonnaise and sour cream in a bowl. To serve, spoon 2 Tbsp. sauce on each plate and top with a chicken quarter.
