A marinade of roasted red bell peppers and citrus juices keeps the chicken moist as it cooks on the grill to perfection. Then, the remaining marinade is boiled down to make a delicious and flavorful sauce that gets a touch of butter at the end.
Place the bell peppers directly on a gas stove over high heat. Char until black and blistered on all sides, turning using tongs. Remove from the heat and place in a paper bag. When cool, gently rub off the skins, and seed the peppers.
Combine the bell peppers, lemon juice and zest, orange juice and zest, garlic, olive oil, juniper berries, thyme, salt, and pepper in a blender and blend until smooth. Place the chicken breasts in a container and pour the marinade over. Refrigerate overnight.
The next day, preheat a gas grill or cast-iron grill pan over medium heat.
Remove the chicken from the marinade and save the marinade. Grill the chicken until it reaches an internal temperature of 165 degrees, about 5-8 minutes per side. Remove from the heat and let rest for at least 5 minutes.
Meanwhile, heat the reserved marinade in saucepan until it comes to a boil. Stir in the butter. Slice the chicken and serve drizzled with the heated marinade.