Place seeded dried peppers in a small sauce pan and cover with water. Bring to a simmer and poach until tender, about 10 minutes; drain. (If you're sensitive to spicy-hot flavors, add peppers sparingly.) In a large skillet over medium-high heat, add olive oil. Add onion, garlic, chipotle peppers, cumin and oregano and saute until onion is tender. Add drained peppers, tomatoes and reserved tomato juice.
Bring to a simmer and cook, uncovered, until thickened, about 45 minutes; cool. When cool enough to handle, puree in batches in a food processor fitted with the metal blade or blender. Strain if smooth sauce is desired. (I did not strain.) Add cilantro and kosher salt. Makes about 4 cups sauce.
Pickled chipotle chili peppers can be found in markets selling Mexican foods. If unavailable, and a hot sauce is desired, use 1 or 2 additional dried red peppers. Poach them and add as directed in recipe. But be careful not to get the sauce too hot.
