Soak the corn husks

• Rinse the corn husks well to remove any dust or debris.
• Soak them in hot water for at least 4 hours or overnight.
• Drain and set aside.

Simmer the pork

• In a large pot, combine the pork shoulder, half the onion, garlic cloves, bay leaf and chicken bouillon with water.
• Simmer on medium low for 3 hours or until the pork is tender.
• Reserve the cooking broth.

Shred the pork

• Once the pork is done, remove it from the pot and shred it.
• Set aside and keep the broth.

Make the salsa roja

• Boil the remaining onion, guajillo chiles, pasilla chiles, garlic cloves and chile de árbol (if using) for 5 minutes.
• Transfer the cooked chiles to a blender with some of the cooking liquid and salt to taste.
• Blend well and save about a cup of salsa for the masa.

Cook the filling

• Heat a little pork lard over medium heat, add the shredded meat and cook for 10 minutes.
• Add the salsa and simmer on low for 30 minutes.
• Taste for salt — the filling should be saltier than the masa.

Prepare the masa base

• Mix the masa with the baking powder and salt.
• Add broth gradually until the masa is no longer dry, using water if you run out.
• The texture should be slightly wetter than play dough.

Whip the lard

• Whip the pork lard until doubled in size.

Finish the masa

• Add the whipped lard to the masa and mix until fully incorporated.
• Add the reserved salsa and mix until fully combined.
• If needed, add broth or water until the masa is easily spreadable with your hands or a spoon.
• Taste everything and adjust the seasoning.

Assemble the tamales

• Fill the steamer pot with water up to the line and add the steamer basket.
• Spread masa on a corn husk, add filling and fold.
• Stand the tamales upright in the pot so the filling doesn't fall out.

Cover and steam

• Cover the tamales with the remaining corn husks or aluminum foil, and optionally a clean kitchen towel to absorb liquid.
• Cover and steam on high for 1 hour and 30 minutes.
• Turn off the stove and let sit 30 minutes before serving.