Cut beef against the grain at a diagonal with a sharp knife as thinly as possible. Place in large bowl.
Sprinkle salt, ground pepper, ground ginger, and garlic powder, and drizzle sesame oil over the top of sliced beef.
Mix well and place bowl in the refrigerator.
In the meantime, cook 1½ cups (300g) of long grain rice in the rice cooker or on the stove. This should take about 15 minutes and it will give you 4 cups cooked rice.
While rice is cooking, cut broccoli into florets. Peel the stems and cut into slices. Also, cut red bell pepper into thin strips.
Once rice is cooked, drizzle 1 tablespoon sesame oil and sprinkle 1 teaspoon sesame seeds and green onions over cooked rice. Gently mix rice with a spatula.
Spoon flavored rice into deep sheet pan leaving the middle empty.
Arrange broccoli florets on each side of the rice to separate rice from beef and place a few of the florets and bell pepper strips over the rice.
Preheat convection oven to 400⁰F/200⁰C or regular oven to 425⁰F/220⁰C.
Remove beef from refrigerator. Mix remaining broccoli florets into the bowl. Transfer marinated beef slices and broccoli florets to the middle of the sheet pan.
Place sheet pan into preheated oven and bake for 20 minutes.
While sheet pan is in the oven, combine all sauce ingredients except cornstarch in a small sauce pan. Bring sauce to a boil. Add cornstarch mixture and let sauce thicken. Set aside.
After 15 minutes of cooking, remove sheet pan from oven. Drizzle half the sauce over the beef. Return to the oven and let it finish cooking for the remaining 5 minutes.
Remove sheet pan from the oven. Drizzle remaining half of the sauce and sprinkle 1 teaspoon sesame seeds over the beef (and rice if desired).