Season the steak with salt and pepper. Grill the steak on a cast iron skillet over medium high heat until to your desired doneness. Remove from the skillet and set aside to rest.
Add the remaining 1/2 tablespoon of oil in a skillet, saute the spinach with a little bit of salt until wilted. Remove the spinach from skillet and set aside. Rest the steak for 5-10 minutes. Cut into thin strips.
Bring the skillet over medium heat again. Spread rice evenly in a skillet, and top with beef slices and the spinach. Drizzle the sauce, about 3-4 tablespoon.
Let the whole thing sizzle for 1 minute. Start tossing together to coat everything with the sauce and cook for another 1 minute. Taste and add more sauce if needed.
When everything is all mixed, remove the skillet from the heat. Drizzle a little more sesame oil and sesame seeds as you desire. Serve immediately.