Place the beef strips in a large bowl or resealable plastic bag. In a blender or food processor, combine the onion, garlic, chipotle chile, adobo sauce, chile powder, cumin, oregano, olive oil, salt, pepper, and water. Blend until smooth. Pour the flank steak marinade over the meat and stir or seal the bag and massage the bag to thoroughly coat and combine. Marinate at room temperature for 30 minutes or cover and refrigerate for up to 24 hours.