Cut dried ancho or dried New Mexico red peppers and, if using, dried chipotle peppers. Open peppers; discard stems and seeds. Cut peppers into small pieces. Bring water to boiling; remove from heat. Add peppers and let stand for 45 to 60 minutes to soften. Do not drain.

Meanwhile, in a large skillet cook onion, oregano, and garlic in hot oil for 3 minutes. Remove from heat; set aside.

Place half of the undrained dried peppers (and canned chipotle peppers, if using) and half of the chopped tomatoes in a food processor bowl or blender container. Cover and process or blend until nearly smooth. Strain through a fine sieve to remove pepper skins and tomato skins and seeds; discard skins and seeds. Repeat blending and straining with remaining peppers and tomatoes. Add strained mixture to onion mixture in skillet along with salt and cumin.

Bring to boiling. Reduce heat and simmer, uncovered, for 20 to 25 minutes or to desired consistency. Serve with huevos rancheros, enchiladas, tamales, or grilled meats and poultry. Makes about 2 cups.

Spoon sauce into an airtight storage container. Cover and chill for up to 1 week.