Fill a large bowl with water, and microwave it until the water is very hot, about 3 minutes. Remove bowl from microwave and submerge the rice noodles in the water. Let soak for about 45 minutes.
Once the noodles have been soaking for 30 minutes, start to prepare the beef:
In a large skillet, saute the sliced onions and the beef over medium heat. Cook, stirring often, until done. Combine the gluten free teriyaki sauce, the tamari sauce, the ginger, and the red pepper flakes in a small bowl, and whisk together. Pour the sauce into the skillet. Stir well.
Add the broccoli to the skillet.
Microwave the noodles in water for 2-3 minutes. Drain. Add the noodles to the skillet with the broccoli, beef, and sauce. Stir to coat.