Slice the flank steak against the grain into very thin strips to ensure maximum tenderness.
In a medium bowl, whisk together the tamari, toasted sesame oil, grated Asian pear, grated ginger, minced garlic, coconut sugar, and black pepper.
Toss the beef in the marinade and refrigerate for at least 30 minutes to allow the enzymes in the pear to tenderize the meat.
Heat a large cast-iron skillet or wok over high heat until it is smoking slightly.
Add the beef in a single layer, working in batches if necessary, and sear for 2-3 minutes until deeply browned and caramelized.
Remove the beef from the pan and quickly sauté the sliced onions and carrots in the remaining juices until they are crisp-tender.
Return the beef to the pan, toss with the sliced scallions, and garnish with sesame seeds before serving.