Preheat oven to 425. Line a rimmed baking sheet with parchment paper for easy cleanup. Add cubed steak to one bowl and broccoli florets to another. Combine the coconut aminos, garlic, sesame oil, rice vinegar, ginger, crushed red pepper, and salt in a bowl and mix well. Pour half of the mixture over the steak, and the remaining half over the broccoli. Mix both well.
Use tongs to remove the steak from the marinade and place it on the baking sheet. Place broccoli onto the baking sheet drizzled with any remaining sauce from the bowl. Spread everything out evenly and bake for 12-14 minutes or until the steak is cooked to desired doneness. Optional: broil for 1-2 minutes to crisp everything up a bit.
Transfer beef and broccoli to a bowl or plate, and pour any juices from the pan into a small saucepan. Add the 2 tbsp coconut aminos to the pan along with the 1/4 tsp sea salt. Mix the arrowroot powder and water together to create a slurry. Bring the pot to a boil and add the slurry. Reduce heat to medium and stir until thickened.
Serve the beef and broccoli over cauliflower rice with the extra sauce, sesame seeds, and green onions if desired.