Place pork belly in a baking dish and rub evenly with granulated sugar and kosher salt. Cover with plastic wrap and refrigerate for at least 12hours and up to 24 hours.
Remove from refrigerator and discard plastic wrap, pat dry, and remove any liquid that has accumulated. Rub with ancho chili powder. Preheat oven to 450 degrees. Roast pork belly for 30 minutes, then lower heat to 275 degrees and roast for 1 hour more, until pork belly is tender.
Let pork belly cool slightly, then slice into approximately ½"slices. If you want perfectly clean slices: cool pork belly completely, then remove from baking dish and wrap in aluminum foil. Refrigerate until cold. Slice pork belly, then reheat in oven at 275 degrees wrapped in aluminum foil until heated through.
Top tortillas with a couple slices of pork belly, chopped avocado, ancho chili roasted pineapple, pickled onions, drizzle with chipotle aioli and a sprinkle of que so fresco and cilantro. Serve with lime wedges and preferably a margarita. Devour.