DO-AHEAD TIP: Marinate chicken overnight or for at least 4 hours (see recipe).
In a medium bowl, whisk together all ingredients except chicken and ghee (or coconut oil).
Place chicken in a large zipper-topped plastic bag and pour grapefruit mixture over the top; seal bag and refrigerate overnight or for at least 4 hours. At time of cooking, melt the ghee (or coconut oil) in a large skillet over medium-high heat.
Remove chicken from marinade (reserving marinade) and place in skillet. Cook for 4 to 6 minutes per side or until juices run clear; remove from skillet and keep warm. Add reserved marinade to the skillet.
Reduce heat to medium-low; whisk mixture for a couple minutes then allow it to simmer for about 5 minutes before serving over the chicken.