Dry toast guajillo and arbol chiles in medium saucepan over medium heat until fragrant. Allow chiles to cool; remove stems and seeds. Soak chiles in boiling water 20 minutes or until softened.
Heat olive oil in medium saucepan over medium-high heat. Add onions and salt; sauté until onions just begin to brown.
Reduce heat to low; stir in garlic, cumin and coriander. Cook 1 minute.
Add butter sauce to onion mixture; simmer over medium heat 4-5 minutes or until sauce reaches 165°f.
Drain chiles; place chiles into pitcher of high-speed blender. Add onion mixture, puree until smooth.
Add vinegar to pitcher; pulse to combine.
Hold hot until service or cool to store refrigerated until next service.
