Heat 2–3 tablespoons of oil in a skillet over medium heat. Add the guajillo and árbol chiles, tomatoes, 1/3 onion, and garlic. Fry until the tomatoes are blistered and the chiles are fragrant, about 4–6 minutes. Watch closely so nothing burns.

Transfer the fried chiles, tomatoes, onion, and garlic to a blender. Add a few tablespoons of water and blend until smooth and homogeneous. Strain if you prefer a finer salsa.

Return a tablespoon of the frying oil to the skillet. Pour in the blended salsa and cook over medium heat, stirring frequently. Season with salt to taste. After it simmers and the flavors combine (3–5 minutes), add the shredded pressed beef rind (chicharrón).

Cook the mixture, stirring, until the salsa reduces and clings to the chicharrón — you want it moist but not soupy and not stuck to the pan. Remove from heat and reserve a few spoonfuls of salsa for serving.

Reheat the remaining frying oil to hot but not smoking. Quickly pass each corn tortilla through the hot oil for just 1–2 seconds per side — this gives them color and a little crispness. Drain briefly and immediately fill each tortilla with 1–2 tablespoons of the chicharrón filling. Set filled tacos aside on a tray.

To make the basket: line a shallow basket or container with a cloth napkin, then a piece of clean plastic, another cloth napkin, and finally paper. Stack the tacos inside and cover to let them 'sweat' for 10–20 minutes; this softens the tortillas and melds flavors.

Serve warm. Spoon the reserved salsa over tacos and garnish with chopped cilantro and onion.