Place roasted red bell peppers in the bowl of a food processor. Add slivered almonds, garlic, cilantro, Parmesan cheese, and lime juice. Pulse until combined. While the food processor is running, slowly pour in olive oil. Season with salt and pepper. Set the pesto aside.
The Mahi Mahi:
In a small bowl, combine brown sugar, cumin, salt, pepper, and chipotle chile powder. Rub each of four 6-ounce mahi mahi fillets with 1 teaspoon olive oil and rub 2 teaspoons of the rub mixture into one side of each fillet.
Heat the grill to high and lay the fillets rub-side down on the grill. Cook until a crust forms, about 2 to 3 minutes. Do not try to move the fish too soon or the crust will tear. Flip each fillet and cook for an additional 3 to 4 minutes, or until the fish is barely cooked through.
Serve each mahi mahi fillet with several tablespoons of the pesto.
Inspired by a Bobby Flay recipe (in Food & Wine Magazine).