Preheat oven to 425 degrees F. Prep roasting pan with a wire rack.
Combine the mayo, mustard, herbs, lemon juice, and pepper in a small bowl.
Rub the chicken down with the mayo herb mixture. Make sure to rub evenly all over and under the skin as well.
Chop garlic and onions in half and stuff inside the chicken cavity with used lemon halves as well. Tie together the legs and place in roasting pan.
Cook for 25 minutes, then reduce heat to 325 and continue to cook for 1 to 1 1/2 hours, until chicken temps at 160 degrees F with a meat thermometer at thickest part. If chicken is browning too much while cooking, cover with aluminum foil.
Remove from oven and let rest, covered, for 15 minutes before slicing and serving.