For the marinade and pork: In a shallow baking dish, whisk together the soy sauce, vinegar, adobo sauce, honey, tamarind paste, cumin and scallions. Add the pork, turning to coat on all sides. Cover and let marinate at room temperature for 1 to 2 hours.
Prepare a charcoal or gas grill for direct high-heat grilling. Lightly oil the grill grates. Remove the pork belly from the marinade and place on the grill. Cook for 2 minutes, then flip and cook for 2 minutes on the other side.
For the tacos: Serve the pork with warm tortillas, cilantro and lime wedges for building tacos.
When cooking meats like pork belly or bacon on the grill, dripping marinade or fat can cause flare-ups. If the flame is small, simply keep an eye on the food. If it's big, either move the food to the cooler zone of your grill (if you have one) or remove the food and cover the grill with its lid until the flare-up dies down.