Season the skirt steak with the beef fajitas seasoning and sugar while you juice the limes. Mix the lime juice with the olive oil and add to a resealable bag or container with the skirt steak. Make sure the beef is fully submerged and refrigerate for at least 3 hours and up to 8-10 hours. Avoid marinating too far beyond that. (Optional: Slice the steak in half with the grain for more manageable pieces on the grill.)

When ready to grill, set the skirt steak out at room temperature while you preheat the Traeger to 500ºF with the lid closed for 15 minutes. You want the grill to be as hot as possible before adding the beef.

Optional: For grilled fajita peppers, add peppers straight to the grill around the back edge when the steak goes on. Be sure to turn every 2-3 minutes.

Add the skirt steak along the front edge of the Traeger grill grates where it's the hottest with direct heat. (Don't go beyond the drip pan.)

Cook for 4-5 minutes before flipping and cooking another 30-60 seconds until a medium internal temperature of 135ºF.

Tent the finished steaks with foil and rest for 5-10 minutes before slicing against the grain and serving with the optional grilled peppers, warmed tortillas, and your favorite beef fajitas fixin's.