Heat your skillet over medium heat and place the guajillo and ancho chiles directly on the surface. Toast them for about 30 seconds per side, pressing gently with your spoon, until they become fragrant and slightly darkened but not burned.

Transfer the toasted chiles to a cutting board and let them cool for about 2 minutes. Use a knife to slit each chile lengthwise and remove the seeds and white membrane inside, then discard the stems.

Place the cleaned chiles in a bowl and cover them completely with hot water from a kettle. Let them soak for 5 to 8 minutes until they are soft and pliable, not mushy.

While the chiles soak, peel and roughly chop the garlic cloves. Measure out the cumin, oregano, black pepper, and salt into a small bowl so they are ready when needed.

Drain the soaked chiles, reserving the soaking liquid, and transfer the chiles to your blender. Add the garlic, cumin, oregano, black pepper, salt, and 1 cup of the reserved soaking liquid.

Blend on high speed for 2 to 3 minutes until the mixture is completely smooth and silky with no chile pieces visible. Add more soaking liquid if needed to help the blender work.

Pour the blended mixture through a fine mesh strainer into a bowl, using the back of a spoon to push it through. This removes remaining chile skin bits and creates a velvety texture.

Heat the vegetable oil in a medium saucepan over medium heat. Pour in the strained chile mixture carefully. Stir constantly for about 3 to 4 minutes until the sauce darkens slightly and becomes fragrant.

Gradually stir in the chicken or vegetable broth starting with 2 cups, then add the remaining cup slowly to reach your desired consistency. Bring to a gentle simmer and cook for 5 minutes, stirring occasionally.

Stir in the apple cider vinegar. Taste and adjust salt as needed, keeping in mind the sauce will concentrate slightly as it cools.