1. In a Ziploc bag combine the orange zest, orange juice, maple syrup, and apple cider vinegar. Add salmon fillets and marinate in the refrigerator for 30 minutes.
2. Preheat oven to 400 degrees.
3. Place salmon fillets in a greased glass dish and bake for 20 minutes.
4. Pour salmon marinade in a saucepan over medium heat and whisk until marinade is thick (almost to a marmalade consistency.)
5. Set aside.
6. Remove salmon from the oven and top with marinade glaze.