Cook the soba noodles according to package directions, drain, and set aside.
Slice the flank steak into very thin strips against the grain and season with sea salt and black pepper.
In a small bowl, whisk together the tamari, honey, minced ginger, and minced garlic to create the stir-fry sauce.
Heat the toasted sesame oil in a large skillet or wok over medium-high heat until shimmering.
Add the beef strips to the pan and sear for 2-3 minutes until browned, then remove the beef and set aside on a plate.
Add the broccoli florets and sliced red bell peppers to the same pan, sautéing for 4-5 minutes until tender-crisp.
Return the beef and the cooked noodles to the pan, pour the sauce over the mixture, and toss for 1 minute to coat everything thoroughly.
Garnish the dish with sesame seeds and serve immediately.