Preheat your oven to 350°F and arrange your arbol peppers on a baking sheet. Roast for 15 minutes then remove from heat and allow to cool before handling.
In a food processor or blender, blend the roasted arbol peppers until smooth.
In a pan over medium heat, sauté bell pepper, celery, carrot and onion for 5 minutes until softened.
Add the arbol pepper puree to the cooked vegetables and stir to combine.
Incorporate cilantro, cumin powder, chilli powder, salt & pepper into the pan and blend together.
Pour over water and vinegar to the pan then bring to a gentle simmer. Simmer for 10 minutes, stirring intermittently.
Taste the sauce and adjust seasoning if necessary before taking off heat and allowing to cool.
Serve immediately or store in an airtight container in the refrigerator for up to 2 weeks.