Place a large skillet over medium-high heat. Add the ground beef and diced onion. Cook for about 6 to 7 minutes, breaking the beef apart as it cooks, until the meat is fully browned and no longer pink.
While the beef is cooking, prepare the sauce. In a small bowl, combine the soy sauce (or tamari), sesame oil, rice vinegar, fish sauce, honey (or coconut sugar), arrowroot powder, and water. Whisk until smooth and set aside.
Once the beef is cooked, stir in the minced garlic and grated ginger. Cook for about 1 minute, just until fragrant.
Add the broccoli florets to the skillet. Cover with a lid and allow the broccoli to steam for 3 to 4 minutes. It should turn bright green and remain slightly crisp.
Pour the prepared sauce into the skillet. Stir well to coat the beef and broccoli evenly. Cook uncovered for another 2 to 3 minutes, allowing the sauce to thicken and lightly coat everything. If desired, increase the heat slightly at the end to let the sauce reduce a bit more.
Remove from heat and add optional toppings such as sesame seeds, green onions, or sriracha. Serve over rice, cauliflower rice, or enjoy it on its own for a simple one pan beef and broccoli meal.