PREPARATION
Prepare Marinade: In a small pot, bring chiles and water to a boil. Transfer to a small bowl and let soak at least 30 minutes to soften (place a small plate over the chiles to keep them submerged).
Transfer chiles and their liquid to a blender. Halve the red onion, and chop 1 half and add to blender (reserve remaining half for salsa). Add garlic, vinegar, achiote paste, 3 tablespoons salt, 1 can pineapple and its juice. Blend until smooth.
Prepare Pork: Place pork slices in a large zipper-lock bag. Pour in blended marinade and let sit at room temperature for an hour or keep in the fridge for 3 hours or overnight.
Pour pork and the marinade into the InstantPot. Cook for 30 minutes on high pressure.
Heat your broiler to high with the oven rack in its highest position. Transfer the pork (reserving liquid) using a slotted spoon to a rimmed baking sheet. Broil until slightly charred, about 8 minutes. Transfer pork to a bowl and shred. Season to taste with salt and vinegar.
Prepare Pineapple Salsa: Chop remaining onion and add to a new baking sheet or the same one previously used for the pork. Broil until slightly charred, about 2-3 minutes. Add onion to a bowl with drained pineapple from remaining can, chipotle, and ½ cup fresh cilantro.
Prepare Corn & Bean Salad: In another bowl combine black beans, corn, jalapeño, ½ cup chopped cilantro and garlic. Squeeze the juice of one lime, stir to combine, season to taste with salt.
Serve shredded pork on warm tortillas with pineapple salsa, corn & bean salad, lime wedges and cilantro.