Remove stems and seeds from dried chilies. Toast them in a dry skillet for 1-2 minutes until fragrant (avoid burning).
In a saucepan, add chilies, tomatoes, garlic, onion, and enough water to cover. Simmer for 10 minutes until softened.
Drain water (reserve ½ cup). Transfer chilies, tomatoes, garlic, and onion to a blender. Add cumin, oregano, salt, pepper, and broth. Blend until smooth.
For extra smoothness, strain through a fine-mesh sieve.
Heat oil in a saucepan. Pour in blended sauce and simmer for 8-10 minutes until thickened. Stir in vinegar.
Taste and add more salt or spices if needed.