1. Preheat grill to 350°F.
2. Heat 2 Tbsp vegetable oil in medium skillet over heat. Add onions and sauté two minutes.
3. Stir in mangoes, garlic powder, peppers, mustard, honey and vinegar. Cook 3-4 minutes.
4. Remove from heat and pour into a food processor.
5. Puree until smooth, remove from food processor and set aside.
6. Divide glaze into two small bowls and set aside.
7. Season fish with salt and pepper on both sides.
8. Brush fish with remaining 2 Tbsp vegetable oil.
9. Grill 6-7 minutes. Turn fish and grill an additional 3-4 minutes.
10. Brush fish with some of the mango glaze and cook an additional 3 minutes. Discard remaining glaze from bowl.
12. Remove from grill and serve with the remaining bowl of mango glaze on side.
Tip: Serve additional glaze on the side as a condiment. This glaze can also be made ahead of time and kept in the refrigerator for up to two weeks. This fish pairs extremely well with simply steamed vegetables and rice.