Add olive oil. When hot add onion and peppers and cook until they soften, about 8 minutes. Add the garlic, chili powder, and cumin, and cook 1 minute more. Add the plum tomatoes and salt. Reduce heat to medium-low, and cook for 5 minutes more.
Transfer the mixture to a blender or food processor fitted with the metal blade and pulse until just smooth. Season to taste with chipoltes en adobo.