Slice the flank steak into very thin strips against the grain to ensure maximum tenderness.
In a small bowl, whisk together the coconut aminos, toasted sesame oil, minced garlic, and grated ginger.
Heat the avocado oil in a large skillet or wok over medium-high heat until shimmering.
Add the beef strips in a single layer, seasoning with sea salt and black pepper, and sear for 2 minutes until browned.
Remove the beef from the skillet and set aside; add the broccoli florets and sliced red bell pepper to the same pan.
Add a tablespoon of water to the pan and cover for 2 minutes to lightly steam the vegetables until they are bright green and tender-crisp.
Return the beef to the skillet, pour the sauce over the mixture, and toss for 1 minute until the sauce thickens and coats everything.
Serve immediately, garnished with a sprinkle of sesame seeds.