Real Homemade Tamales

Place pork, onion, and garlic in a Dutch oven. Add enough water to cover; bring to a boil over medium-high heat. Reduce the heat to low; simmer pork until cooked through and tender, about 2 hours.

Remove stems and seeds from chiles; transfer to a medium saucepan with 2 cups water. Simmer, uncovered, for 20 minutes. Remove from heat to cool.

Transfer chiles and cooking liquid to a blender; blend until smooth. Strain sauce through a fine-mesh sieve into a bowl; stir in salt. Discard contents of strainer.