Heat a medium skillet over medium-high heat. Rub the steak with 1 tablespoon of the sesame oil and sprinkle generously with salt. Cook the steak until browned and medium-rare, 3 to 4 minutes per side. Remove to a plate, cover with foil and let rest for 5 minutes.
Meanwhile, whisk together the garlic, soy sauce, vinegar, gochujang and the remaining 1 teaspoon sesame oil in a small bowl.
Arrange the cabbage, spring onions, noodles and peanuts in two serving bowls.
Thinly slice the steak against the grain and divide between the bowls. Pour the sesame dressing over the top and garnish with cilantro leaves.