Fill a bowl with hot water and submerge the husks to soften.
Meanwhile, in a large saucepan, mix 2 tbsp. chili powder and the tomato paste into 6 cups cold water; add the pork. Bring to a boil, cover and reduce the heat to low. Simmer until the meat is very tender, about 3 hours. Transfer to a plate; reserve the broth. Shred the meat and transfer to a bowl.
In a medium saucepan, heat 1/4 cup oil over medium heat. Stir in 1 tbsp. chili powder, 1 1/2 tsp. salt, cumin and garlic powder; cook for about 30 seconds. Stir in 1 cup of the reserved broth; combine with the meat.
In a large bowl, mix the masa, the remaining 1 tbsp. chili powder, 1 1/4 tsp. salt and 1/2 tsp. pepper. Stir in 3 1/2 cups of the broth. Using a wooden spoon, beat in the remaining 1 1/2 cups oil.
Drain the husks; pat dry. Working with one husk at a time, spread about 1/4 cup of the masa mixture down the center. Top with 2 tbsp. meat. Fold the long sides of the husk together and roll into a skinny log. Fold up the bottom, creating a package that is open on top. Loosely tie three tamales together with a piece of kitchen string, making 12 bundles.
Place a heatproof 2-cup glass measuring cup upside down in the center of an 8-qt. stockpot. Stand the tamale bundles, open ends up, around the cup. Fill the pot with the remaining broth and water to reach halfway up the sides of the tamales. Bring to a boil, cover and reduce the heat to medium-low. Simmer until the masa is firm and pulls away from the husk easily, about 1 hour. Serve hot, with some of the cooking liquid.