Place the pork in a large pot, cover with water, and bring to a boil. Reduce heat and simmer until the meat is tender, about 1 hour.
Remove the pork from the pot and shred the meat using two forks.
Prepare the masa by beating the vegetable shortening until fluffy. Add the masa harina, baking powder, and gradually mix in the chicken broth until smooth.
Mix the shredded pork with chili powder and season with salt to taste.
Spread a thin layer of masa on each corn husk, add a spoonful of pork in the center, roll up the husk carefully, folding the bottom end.
Place assembled tamales upright in a steamer. Steam for about 90 minutes, until the masa separates easily from the husk.