1Heat grill pan over medium-high heat. Drizzle oil into pan, then add chiles. Cover; cook 5 minutes, turning occasionally, until softened.
2Cut top off each chile; place chiles in blender. Add vinegar, garlic and salt. Cover; blend on high speed until pureed.
3Store sauce tightly covered in jars or resealable containers in refrigerator up to 2 weeks.