In a bowl, combine the olive oil, the cumin,onion powder, paprika salt and pepper. Add the shrimp, stir to coat and refrigerate for 15 minutes.
Heat a grill over medium-high heat. Remove the shrimp from the marinade and discard the marinade. Thread the shrimp onto skewers. Arrange the skewers on the grill and cook for 2 to 3 minutes per side.
Serve immediately with the mango sauce on top or the side.
Mango Sauce
Heat the butter in a small sauce pan, add the onion, garlic and red pepper flakes and cook for a couple of minutes. Add the rest of the sauce ingredients and cook for about 5 minutes over medium heat. Set aside and serve with the shrimp skewers.