Slice ribeye into ¼ inch strips and place in a large food storage bag. (Tip, place steak in the freezer for 20 – 30 minutes before slicing to make it easier.)
In a medium mixing bowl, combine the Marukan Sudachi Ponzu, pear, sugar, sesame oil, gochujang, garlic, and ginger. Pour into the large food storage bag along with the steak, massage gently to coat the steak, and marinate for 2 hours or up to overnight, turning the bag occasionally.
Heat a large cast iron skillet over medium-high heat. Add one tablespoon of oil and let it heat for a moment. Working in batches, add the steak to the pan in a single layer. Cook undisturbed, for 1 – 3 minutes then flip and cook on the other side for 1 – 3 minutes, don’t overcook. Remove from the pan. Repeat with the remaining oil and steak.
Serve immediately in bowls over rice with the cucumber salad, kimchi, and lettuce leaves if desired. Garnish with green onions and sesame seeds.