PLACE all salsa ingredients - except the cilantro - into a large sauce pot, add water to cover and bring to a simmer. Cook the ingredients until soft, about 8 to 10 minutes. Let cool.
REMOVE all ingredients, using a slotted spoon, to the pitcher of an electric blender, add cilantro and puree until smooth. Add a small amount of the cooking liquid to adjust the consistency. Reserve.
MIX all cure ingredients.
CARNITAS DE PATO
RUB duck liberally with cure mix, place them in a large dish and refrigerate for 2 hours. After 2 hours rinse duck under cold running water and pat dry with paper towels.
PREHEAT oven to 300ºF.
MELT lard or duck fat in a large roasting pan on the stove over medium heat. Add the duck and all other aromatics bring to a simmer, cover with aluminum foil and place in oven for approximately 2 hours, until tender and falling from the bone.
REMOVE from oven, place roasting pan back on the stove and heat on the burner until duck skin becomes brown and crispy on the outside and let cool in the liquid. Remove duck legs from the liquid and let drain on a baking rack. Pull duck meat and skin from the bone and roughly chop.
HEAT a cast iron skillet over medium high heat, add vegetable oil and pulled duck and cook until crispy and heated through.
HEAT each tortilla on both sides, place 2 ounces of duck in the center of each, drizzle with Serrano salsa and sprinkle on onions, cilantro and cheese. Enjoy.