Soak corn husks in warm water until soft and pliable. Set aside.
Cook pork in lightly salted water until fork-tender. Shred and reserve cooking broth.
Remove stems and seeds from dried chiles. Toast briefly, then soak in hot water until softened.
Blend chiles with onion, garlic, cumin, black pepper, and salt until smooth.
Simmer the red sauce for 10 minutes, then stir in shredded pork. Set aside.
In a large bowl, beat lard or shortening until fluffy. Mix in masa harina, baking powder, and salt.
Gradually add warm broth and mix until masa is soft and spreadable.
Spread masa onto the smooth side of a corn husk. Add pork filling down the center.
Fold sides inward and fold the bottom up to seal.
Stand tamales upright in a steamer and steam for 90 minutes, or until the masa pulls away easily from the husk.
Let tamales rest for 10 minutes before serving.