2In a blender, combine the rehydrated Guajillo chiles, Ancho chiles, Garlic, 100g White onion, Lime juice, Achiote paste, Orange juice, Cumin, Mexican oregano, Salt, and Black pepper. Blend until a smooth paste forms, adding a tablespoon or two of the reserved chile soaking liquid if needed to achieve a smooth consistency.
3Pat the Red snapper dry with paper towels. Make several diagonal slits on the skin side of the fish to allow the marinade to penetrate. Generously spread the chile marinade all over the Red snapper, ensuring it gets into the slits and covers both sides. Marinate for at least 30 minutes at room temperature, or up to 2 hours in the refrigerator.