Place pork shoulder, ribs, onion, garlic, bay leaf, and salt in a Dutch oven.

Cover with water.

Bring to a boil and cook, covered, over medium heat until the meat is barely tender (about 45 minutes).

Simmer slightly covered until the meat is barely tender (about 45 minutes).

Remove the cover and increase heat to medium-high.

Cook until the liquid has evaporated (about 20 minutes).

Let the carnitas fry in its own fat until browned and crispy (about 30 minutes).

Remove and drain on paper towels.

Warm tortillas on a seasoned comal set over medium heat.

Remove and keep warm in a tortilla warmer or a kitchen towel.

Remove the stems of the arbol chiles (do not remove seeds).

Gently toast the chiles on a comal set over medium heat, turning occasionally and taking care not to burn.

Cover the chiles with hot water and let soak for 15 minutes.

Drain and discard water.

In a small saucepan, cook the tomatillos and garlic with barely enough water to cover.

Cook until the tomatillos are cooked through (about 5 minutes) - do not let them burst open.

Transfer the reconstituted chiles, tomatillos, garlic, and salt into a blender.

Process until smooth, adding some liquid from the tomatillos to thin.

Season with salt to taste.

Rinse the sliced red onion in hot water.

Place the onions in a non-reactive glass jar and add orange juice, apple cider vinegar, habanero chile, oregano, and salt.

Press the onions down to cover with the juice, ensuring they are submerged.

Marinate for at least 12 hours.

Store in the refrigerator for up to 2 weeks.

Assemble the tacos with carnitas, salsa de chile de arbol, pickled onions, guacamole and your choice of salsa.