Slice the flank steak into thin strips against the grain and season with sea salt and black pepper.
Mince the garlic clove and finely grate the fresh ginger.
Heat the avocado oil in a large wok or skillet over high heat until shimmering.
Add the beef strips to the hot pan in a single layer and sear for 2-3 minutes until browned, then remove the beef and set it aside.
In the same pan, add the broccoli florets and sliced red bell pepper, stir-frying for 3-4 minutes until they are tender-crisp.
Return the beef to the pan and add the garlic, ginger, coconut aminos, and toasted sesame oil.
Toss all ingredients together for 1 minute to allow the sauce to thicken and glaze the beef and vegetables.
Remove from heat, garnish with sesame seeds, and serve immediately.