In a small bowl, mix together the ground coriander, ground cumin, smoked paprika, salt, and black pepper.

Pat the flat iron steak dry with paper towels. Rub the olive oil over the steak, then generously coat both sides with the spice mixture, pressing it into the meat to adhere.

In another bowl, combine the softened butter, harissa paste, and lemon juice. Mix until well blended. Set aside.

Heat a grill or cast-iron skillet over medium-high heat. Once hot, add the seasoned flat iron steak. Cook for about 4-5 minutes on each side for medium-rare, or until your desired doneness is reached. Use a meat thermometer for accuracy (130°F for medium-rare).

Remove the steak from the heat and let it rest for 5-10 minutes. This allows the juices to redistribute.

Slice the steak against the grain. Top with a dollop of the spicy harissa-infused butter and garnish with fresh cilantro. Enjoy with your favorite sides!