With flat iron steak you have all the tenderness of filet, but you must provide the flavor with marinades or rubs.
Lay steaks out on a platter and allow to come to room temperature, about 30 minutes.
Preheat an outdoor grill for high heat and lightly oil grate.
Preheat oven to 400 degrees F (200 degrees C).
Whisk together the olive oil, pepper, salt, garlic powder, onion powder, cayenne pepper, brown sugar, and lemon juice in a small bowl. Evenly rub one side of each steak with the mixture.
Lay the steaks on the hot grill with the seasoned-side facing up for 2 minutes. Flip and sear the seasoned side about 2 minutes.
Transfer steaks to preheated oven; bake to desired doneness, seasoned-side up, 8 to 10 minutes for medium-well. Allow to rest 3 to 4 minutes before serving.
Per Serving: 393 calories; protein 35.3g; carbohydrates 3.6g; fat 26.5g; cholesterol 116mg; sodium 1070.8mg.