Slice the flank steak against the grain into thin, bite-sized strips and season with sea salt and black pepper.
In a small bowl, whisk together the coconut aminos, grated fresh ginger, and minced garlic to create the stir-fry sauce base.
Heat the avocado oil in a large skillet or wok over high heat until shimmering.
Add the beef strips in a single layer and sear for 2 minutes until browned, then remove the beef from the pan and set aside.
In the same pan, add the broccoli florets and sliced red bell pepper with a splash of water, covering for 2 minutes to steam-tenderize.
Remove the lid, return the beef to the pan, and pour in the sauce mixture and toasted sesame oil.
Toss everything together for 1 minute until the sauce thickens slightly and coats the ingredients beautifully.
Transfer to a plate and garnish with sesame seeds before serving.