Fajita Tacos Al Carbon (Charcoal-grilled fajitas & flour tortillas) 1. Sprinkle fajitas (skirt, flank, thin sirloin, etc.) generously with Fajita Seasoning. 2. Let fajitas stand 30 minutes for flavor development and tenderization (maximum tenderizing occurs when left refrigerated overnight, covered overnight. 3. Sear the fajitas quickly over a hot grill or charcoal fire to seal in the juices, then allow to cook until just done. 4. Slice the meat across the grain. Place on hot flour tortillas. Garnish with guacamole, cheese and picante sauce.