Season both side of the rib eye steak with soy sauce and steak seasoning. Cover and refrigerate at least 1 hour to overnight.
Preheat an outdoor grill for medium-high heat and lightly oil the grate.
Grill steak on preheated grill until firm, reddish-pink, and juicy in the center, about 6 minutes per side. An instant-read thermometer inserted into the center should read 130 degrees F (54 degrees C). Transfer steak to a platter, sprinkle with lemon juice, and cover loosely with aluminum foil. Allow meat to rest for about 10 minutes, then cut into strips.
Whisk rice vinegar, olive oil, sugar, sesame oil, garlic powder, and red pepper flakes together in a small bowl. Combine lettuce, cucumber, avocado, tomato, carrot, red onion, and steak strips in a large bowl. Pour rice vinegar dressing over salad and toss to coat. Sprinkle with sesame seeds to serve.