Heat a large cast-iron skillet over medium-high heat. Sprinkle the steaks with the chile flakes and some salt and pepper and coat with 2 tablespoons of the olive oil. When the skillet starts to smoke, add the steaks, raise the heat slightly and cook, rotating the steaks every 2 to 3 minutes to make sure they have an even char on all sides, 10 to 12 minutes total. Set the steaks aside, uncovered, to rest. This allows all the juices to redistribute into the steak.
Wipe out the skillet and set it over medium-high heat. Add 2 of the lime halves to the skillet cut-side down and cook until heavily charred, 3 to 5 minutes. Set aside for serving.
Combine 1 bunch of the cilantro, the juice of the remaining lime halves, some salt and pepper and remaining 1 tablespoon olive oil in a food processor and process until a paste forms.
Add the sour cream to a medium bowl and grate in the garlic with a rasp grater. Gently fold in the cilantro paste. Set aside.
Over an open flame, heat the tortillas 3 at a time for 20 to 30 seconds on each side.
Slice the steak against the grain. Spread the sour cream mixture on a wide platter and arrange the sliced steak on top. Garnish with the grilled lime halves and remaining cilantro and sprinkle with the chile-lime seasoning if using. Serve with the tortillas.