Begin by stemming and lightly shaking out the seeds from arbol chiles. Toast them in a medium skillet over medium heat for 2-3 minutes.

Once toasted, bring a saucepan of water to a boil, then turn off the heat. Add the toasted chiles to soak for 15 minutes.

While the chiles soak, heat olive oil in a skillet and cook roughly chopped white onion for 3-4 minutes until translucent. Add chopped garlic and continue for 1-2 minutes, then add Roma tomatoes and cook for about 5 minutes.

Drain the soaked chiles and add them to a blender with the sautéed onion mixture, lime juice, and salt. Blend until smooth, adjusting with reserved chile water if necessary.

Taste the salsa and adjust seasoning with more salt or lime juice as needed. Add chopped tomatoes to mellow the flavor if too intense.