Mollejas de Res

Cut the sweetbreads into small to medium-sized pieces, cutting through the open spaces, and put them in a bowl; squiz the limes and the orange juice on it, add the sazón packet and the paprika, minced garlic, onion slices, and season with salt, and black pepper; mix everything well and push the sweetbreads down to keep them the best submerged possible; cover with plastic and let it marinate in the fridge for at least 2 hours, overnight is way better. In a skillet on medium to low heat, add the beef tallow or cooking oil, and add the sweetbreads; sear them on both sides, getting a slightly charred sear, then add the rest of the marinade and the onions and cook on low heat until the liquid reduces. This is really good in a taco; slice up the mollejas and put it in a warm corn tortilla with salsa, caramelized onions, onions, and cilantro.