1Place the tomatillos, tomatoes, oil, chili pepper, shallots, cilantro, vinegar, garlic powder, and salt in a large saucepan over medium-high heat. Bring to a boil, then reduce heat to medium-low and simmer for 15 to 20 minutes until the tomatillos have softened. Pour into a blender, and puree until smooth. Chill and serve.