Heat two tbsp of oil on a frying pan. Cut the roughly the tomatoes and onion. Place them on the oil and start frying them. Toss them from time to time.
After 5 min add the garlic and continue tossing for another 5 minutes. Then remove the vegetables from the frying pan and set aside.
Using the same fryin pan, add one tbsp of oil and fry the arbol chillies for 3 minutes. Remove them from the heat.
Place all the ingredients in a blender. Add the salt and start blending, add the rest of the oil while the salsa is blending. It has to be smooth and runny. Enjoy it with your favourite taco recipe.