Thread garlic cloves onto a metal skewer and grill directly over the flame of a gas grill until completely blackened on all sides, 3 to 4 minutes. Alternatively, toss in a dry skillet over high heat until blackened. Peel blackened skins when cool enough to handle.

Heat oil or lard in a skillet over medium heat until shimmering. Add achiote, oregano, cloves, cinnamon, black peppercorns, cumin, and allspice and cook, tossing and stirring, until fragrant, about 2 minutes. Transfer to a blender along with peeled garlic, bitter-orange juice, vinegar, soy sauce, and a big pinch of salt. Blend until smooth. Season to taste with more salt. It should be quite salty and have a consistency like ketchup. If too thick, thin it with water until it flows slowly.

Pour marinade over meat and rub it in with your hands. Cover, refrigerate, and let it rest at least 1 hour and up to overnight.

Lay out 2 to 3 overlapping banana leaves on a work surface. Place 1 piece of pork in the center and layer with some of the tomatoes, bell pepper, onion, and bay leaves.

Form a tight parcel by folding the bottom side up and the top side down, then rolling in the sides. Secure parcel with kitchen twine and transfer pork to an oven-safe baking sheet or disposable aluminum baking tray. Repeat with remaining pork and banana leaves.

Light ¾ chimney full of charcoal. When all the charcoal is lit and covered with gray ash, pour out and arrange coals on one side of charcoal grate. Set cooking grate in place, cover grill, and allow to preheat for 5 minutes. Alternatively, set half the burners on a gas grill to medium-high, cover, and preheat for 10 minutes.

Place a few large hardwood chunks on coals (no need to soak). Place aluminum tray or baking sheet on the side opposite the fire and close lid. Smoke pork, aiming for a temperature between 250 and 300°F inside the chamber the whole time, until a metal skewer inserted into pork shows no resistance, 4 to 5 hours total. (Adjust heat by adding coals and/or adjusting the air vents.) Add extra wood chunks to coals once per hour.

Remove pork from grill and transfer parcels to a deep platter or shallow bowl. Unwrap banana leaves, shred pork with two forks, stir it into drippings, stuff it into tortillas with pickled red onions and salsa, and serve immediately.