Remove the stems from the dried chilies and shake out some of the seeds if a milder salsa is preferred.
Toast the chilies in a dry skillet for 20 to 30 seconds per side, then soak them in hot water.
Simmer the tomatillos, onion, and garlic in water for about 8 minutes until softened.
Drain the vegetables and chilies, reserving some of the cooking liquid for adjusting the salsa.
Blend the tomatillos, chilies, onion, garlic, cumin, lime juice, salt, and ½ cup water until smooth.
Add more reserved liquid if needed, cool the salsa completely, and adjust the salt or lime before serving.
