For the pork: Melt the lard in a large pot over medium heat. Squeeze the juice from the citrus fruits into the lard along with the skins. Add the pork shoulder, bay leaf, onions and salt. Turn the heat down to medium-low, cover the pot and cook the pork, about 1 hour and 45 minutes.
In the meantime, for the pickled vegetables: In a non-reactive pot, bring the vinegar, chiles de arbol, salt and peppercorns to a boil. Take off the heat and add the green beans, wax beans, carrots, corn, garlic and jalapenos. Chill in the refrigerator to cool down, at least 1 hour. Will hold in the refrigerator for up to 2 weeks.
For the cactus salad: Heat a grill pan over medium-high heat, add 2 tablespoons of the olive oil and grill the cactus paddles until soft and charred, about 10 minutes. Remove the paddles and set aside. Add the remaining 2 tablespoons olive oil and grill the scallions until just cooked, about 3 minutes. After the cactus and scallions have cooled, dice them up and mix with the tomatoes, chile and lime juice. Season with salt and pepper and reserve.
After the pork has been cooking and is soft, turn the heat up to medium-high and add the cola. Cook until the pork caramelizes, 15 to 20 minutes.
To assemble the carnitas, strain a spoonful of the pork from the fat and serve on a warm corn tortilla. Garnish with the pickled vegetables, the cactus salad and lime wedges.
This recipe was created by a contestant during a cooking competition. It has not been tested for home use.