In a small bowl, combine the softened butter, chopped cilantro, lime zest, and lime juice. Mix until well combined. Place the butter mixture onto a piece of parchment paper, and roll it into a log shape. Twist the ends to seal. Refrigerate until firm, about 30 minutes.

Preheat your grill or a grill pan over medium-high heat. In a spice grinder or mortar and pestle, grind the toasted cumin seeds until fine. In a bowl, mix the ground cumin with Aleppo pepper, salt, and black pepper. Rub the spice mixture generously over both sides of the flat iron steak.

Drizzle the olive oil over the steak, ensuring it’s evenly coated. Place the steak on the preheated grill. Cook for about 4-5 minutes on each side for medium-rare, or to your desired doneness. Remove the steak from the grill and let it rest for 5-10 minutes before slicing.

Slice the steak against the grain and serve it topped with slices of the cilantro-lime compound butter. Allow the butter to melt over the warm steak for added flavor.