Light the Masterbuilt Gravity Series™ 1050 Digital Charcoal Grill + Smoker and set it to 600° F.
Prep the onions–Cut an “X” along the top of the onion going 1/3 of the way down. Stuff the “X” of each onion with a couple sprigs of rosemary, 1 tbsp. of butter cubed, a healthy pinch of kosher salt,and a healthy pinch of black pepper. Wrap onions in tin foil.
Prep the marinade–On the grill, heat 1/4 cup of butter, 1/4 cup of bleu cheese, squeeze half of a lime (approx.1.5 tsp), a pinch of cayenne powder and whisk together well.
Prep the Steak–When ready to cook-season lightly with more kosher salt, black pepper, paprika, and garlic powder. Drizzle steak on both sides with your butter/blue cheese marinade. ProTip–Dry each steak well, salt generously on all sides with kosher salt, put on a wire rack, and let them sit in the fridge exposed for a day or two to dry it out.
Cook the onions–Toss tin foil wrapped onions on the grill. Turn every 5-7 minutes during cooking. Cook for approximately 20 minutes.
Cook the steak–Grill for 5 minutes on each side, basting with blue cheese butter each time you turn.
Garnish steak with cubed butter, bleu cheese crumbles, fresh rosemary, and a squeeze of lime. Cut/tear caramelized onions into hearty chunks.