You will also need: Large re-sealable plastic bag
Add the orange juice, soy sauce, orange marmalade, rice vinegar, ginger powder, garlic and crushed red pepper (if using) to a jar or a medium bowl. Stir well to combine. Give the sauce a good stir right before using too.
Pat the meat dry with a paper towel. Cut the steak into thin slices working against the grain. Sprinkle the beef with the salt.
Add the cornstarch and flour to a large, re-sealable plastic bag. Add the sliced beef and seal it tightly leaving air inside the bag. Shake the bag from side to side and up and down to coat the steak. Massage the bag a bit to separate the pieces and shake again. Do this several times.
Heat the oil in a large, non-stick skillet over medium-high heat. When the oil is hot, but not smoking, add half of the beef.
Arrange the beef in a single layer and cook 2-3 minutes. Use tongs to turn each piece and cook another 1-2 minutes, or until the steak pieces are a golden-brown color.
Remove the steak from the skillet. Use tongs or a slotted spoon and set them on a plate or pan.
Fry the rest of the meat following the same steps. Remove the second batch.
When all of the beef is cooked through lower the heat to medium-low. If there is a pool of oil in the skillet, drain it but do not wash or wipe the pan.
Add the prepared sauce and bring it to a simmer. Cook the sauce for 2-3 minutes, stirring frequently.
Add the beef to the sauce and cook 2-3 minutes or until the beef is coated and the sauce thickens. Stir often and keep it at a simmer. If it starts boiling too vigorously, lower the heat a bit.
Remove the skillet from the heat. Garnish the orange beef with orange zest, sesame seeds and sliced green onions, if desired.