Preheat your oven to 400 F.
Season each chicken breast with sea salt and freshly ground black pepper, and place in a baking dish.
Sea salt and freshly ground black pepper, 4 boneless skinless chicken breasts
In a bowl, mix together the orange zest, orange juice, onion, and raw honey.
2 tbsp. orange zest, 1 cup fresh orange juice, ¼ cup onion, 3 tbsp. raw honey
Pour the liquid into a saucepan and bring to a boil over medium-high heat.
Lower the heat and simmer for 5 to 6 minutes.
Remove the pan from the heat, and whisk in the whole grain and the Dijon mustard.
2 tbsp. Dijon mustard
Pour the orange-mustard sauce over the chicken and place it in the preheated oven.
2 tbsp. whole-grain mustard
Bake in the oven for 40 to 45 minutes.