For the Spiced Duck, mix ancho chile pepper, cardamom, sea salt and pepper in small bowl. Score skin of duck with diagonal cuts. Rub both sides of duck breast with spice rub. Heat medium skillet on medium-low heat. Add duck breast, skin-side down. Cook 15 to 20 minutes or until some fat has melted and skin is browned. Turn duck breast; cook 8 to 11 minutes or until internal temperature reaches 135°F for medium-rare. Remove duck from skillet. Set aside.
Strain duck fat, reserving 2 tablespoons. Wipe skillet clean. Add reserved duck fat, blueberry jam, Port, onion, cardamom and pepper to skillet. Cook on medium heat 7 to 9 minutes or until reduced, stirring occasionally. Add butter; whisk until sauce is thickened. Whisk in lemon juice. With center part of cover removed to let steam escape, puree sauce in blender on high speed until smooth. Set aside.
For the Arepas, preheat oven to 350°F. Mix water, cornmeal, masa harina, 2 tablespoons of the butter, melted, and sea salt in medium bowl until well blended. Divide mixture into 8 portions. Form each into a ball then flatten into a disk, about 2 1/2-inches in diameter and 1/4-inch thick. Melt 3 tablespoons of the remaining butter in large nonstick skillet on medium heat. Add arepas; cook 5 to 6 minutes per side or until golden brown. Add remaining 3 tablespoons butter as necessary. Transfer arepas to parchment paper-lined baking pan. Bake 4 to 5 minutes or until cooked through.
To serve, slice duck breast into thin slices. Place 1 to 2 slices on each arepa. Top with Blueberry Port Sauce. Garnish with cilantro leaf and lemon peel.