Wipe chile peppers with a damp cloth to clean. See the warning for handling instructions.
Break off stems, and remove seeds.
Soak chili peppers in hot water until softened, about an hour.
Taste the soaking water. If it is bitter, replace it with fresh water.
Puree chili pepper and water mixture in a blender
Heat the oil in a pan, add onion, garlic, and seasonings.
Once the onions are cooked, add the chili puree to the pan.
Simmer for 15 minutes.
Return mixture to the blender, and puree. See warning.
Pour sauce through a sieve. Use a spoon to stir and press the mixture against the sieve to extract all the sauce.
Add salt to taste. If the sauce is a little bitter, some sugar can be added to compensate.