Combine the cola, soy sauce, brown sugar, freshly minced garlic, ginger, toasted sesame oil, and red pepper flakes in a bowl, stirring until the brown sugar dissolves completely. This creates a balanced marinade with sweet, salty, and umami flavors. Taste it—the cola should add subtle caramel sweetness without being overpowering. Reserve about 2 tablespoons of the marinade in a separate bowl for basting during cooking, then place the remaining marinade in a shallow dish with the steaks, ensuring they're well coated on both sides. Cover and refrigerate for at least 8 hours, or up to 24 hours for deeper flavor penetration.

Remove the steaks from the refrigerator 30-45 minutes before cooking to bring them closer to room temperature—this ensures more even cooking throughout. While the steaks rest, preheat your oven to 400°F. Chop the green onions into 1/4-inch rounds and set aside for garnish. I like to pat the steaks dry with paper towels just before searing; this helps them brown better and creates a better crust.

Heat the olive oil in a large oven-safe skillet over high heat until it shimmers. Working quickly, place the steaks in the hot skillet and sear for 2 minutes on each side without moving them—this creates a flavorful brown crust. Brush each steak with the reserved marinade from Step 1. Transfer the skillet to the preheated 400°F oven and bake for 5-7 minutes, depending on thickness and your preferred doneness (5 minutes for medium-rare, 7 for medium).

Remove the skillet from the oven and let the steaks rest in the pan for 5 minutes before serving or slicing. This resting period allows the juices to redistribute throughout the meat, keeping it tender and moist. Transfer to a serving plate and garnish with the chopped green onions from Step 2.