Cook the rice (instructions here). Toss the steak in 2 teaspoons soy sauce, sesame oil, ¼ teaspoon salt, and pepper to coat.
Sprinkle the cornstarch (or other starch of choice) all over the steak and toss again to coat.
In a large skillet over medium-high heat, warm 1 tablespoon oil. Once the skillet is hot, add the steak and spread out into an even layer. Let it cook, undisturbed, for about 2 minutes or until browned in spots, then give it a stir and cook for 1-2 more minutes, stirring often, or until mostly cooked through. Transfer back to the plate or bowl or cutting board you tossed it in.
Reduce the heat to medium, then add the remaining 1 tablespoon oil along with the white/light green scallions, celery or fennel, lemon zest, and remaining ¼ teaspoon salt. Stir everything together and cook for 30 seconds, then pour in ¼ cup water and scrape up anything stuck to the bottom of the skillet.
Cook until the water has evaporated, about 1-2 more minutes. Add the beef back into the skillet along with the asparagus.
Increase the heat back up to medium-high and add the remaining ¼ cup soy sauce and ¼ cup water. Stir everything together, and let it simmer rapidly until the sauce reduces and thickens a bit, about 3-5 more minutes, stirring occasionally. Turn off the heat and stir in half of the dark green scallions.
Serve on top of warm rice and top with the remaining green scallions, sesame seeds, more black pepper, and lemon wedges for squeezing.