Thinly slice the flank steak against the grain into bite-sized strips to ensure maximum tenderness.
Heat one teaspoon of toasted sesame oil in a large skillet or wok over medium-high heat until shimmering.
Add the beef strips to the pan, seasoning with sea salt and black pepper, and sear until browned on all sides.
Remove the beef from the pan and set aside on a plate to rest.
Add the remaining teaspoon of sesame oil to the skillet along with the broccoli florets and sliced red bell pepper.
Stir-fry the vegetables for 3-4 minutes until they are tender-crisp and brightly colored.
Stir in the minced garlic and grated fresh ginger, cooking for 30 seconds until the aroma is released.
Return the cooked beef and any accumulated juices to the pan and pour in the coconut aminos.
Toss everything together for 1 minute to glaze the beef and vegetables in the sauce.
Garnish with toasted sesame seeds and thinly sliced scallions before serving immediately.