If using the Instant Pot method, cut the pork shoulder into 4 or 5 equal pieces; otherwise, leave it whole. Season the meat with the salt.
Cook the pork using one of the three methods below:
Oven Method (Cook Time: 4½ hours)
Preheat the oven to 325°F. Heat the oil in a Dutch oven or enameled cast-iron pot with a lid over medium-high heat. Add the seasoned pork to the pot and sear for 3 to 4 minutes per side, until browned. Once browned, pour 1½ cups of water into the pot, then cover with the lid and transfer to the oven. Cook for 3½ to 4½ hours, until the pork shreds easily.
Set the Instant Pot to Sauté mode and heat the avocado oil. Sear the pork for 2 to 3 minutes per side, working in batches. (If you are short on time, you can skip this step, though it does add more flavor to the pork!) Once seared, return all the pork to the pot, along with ½ cup of water. Put the lid on the Instant Pot, checking to make sure that the pressure valve is sealed, press Pressure Cook or Manual, and then program it to cook for 90 minutes on high pressure. Once the timer goes off, release the pressure manually by slowly turning the pressure valve from sealed to “venting.”
Place the seasoned pork in a 6-quart slow cooker. Cook on low for 8 to 10 hours, until the pork shreds easily.
Once cooked through, shred the meat with 2 forks, removing the excess fat.
For the Crust
Preheat the oven to 375°F.
To peel the plantains, slice off the ends, then, with a small paring knife, score the peel of each plantain lengthwise four times, along the seams. Carefully separate the peel from the plantain, then cut each plantain into thirds. Put the plantains in a food processor or blender.
To the food processor or blender (with the plantains), add the coconut oil and salt and blend until smooth.
Line a cookie sheet with parchment paper or a silicone baking mat and spread the plantain mixture into two 8-inch circles, making the thickness as even as possible.
Bake for 25 to 30 minutes, until the crusts are browned and no longer sticky.
For the Pizza
Preheat the oven to 375 F.
Blend together the mayo, lime juice, and adobo sauce until smooth.
Spread the pork and pineapple onto the pizza crusts, then top with the adobo sauce.
Place the pizzas directly on the oven rack (or on a preheated pizza stone) and bake for 15 minutes, until the pork is browned and the sauce is bubbling.
Garnish with the cilantro and red onion, then slice and serve!