If using a spiralizer, spiralize the broccoli stems. If not, cut into ⅛"-thick planks, then slice into “noodles.”
In a large bowl, whisk hoisin, orange juice, and soy sauce. Add steaks, cover, and refrigerate for 2 hours.
While steaks are marinating, bring a large pot of salted water to a boil and create an ice bath in a large bowl. Boil broccoli florets for about 2 to 3 minutes or until bright green and just tender. Transfer broccoli to the ice bath until cool, then drain.
Remove steaks from the refrigerator and transfer to a plate. Leave the marinade in the bowl.
Heat a large nonstick skillet over high heat and grease with cooking spray. When hot, cook the steaks for about 3 minutes on each side (for medium-rare) or until a thermometer reads 130º in the thickest part of the steaks. Transfer steaks to a cutting board to let rest for 10 minutes, then slice into thin strips.
In a small saucepan over medium-low heat, bring reserved marinade to a boil and simmer until slightly thickened, 2 to 3 minutes.
Add sesame oil to skillet over medium heat. Add onions, garlic, and ginger and cook on high, 1 to 2 minutes. Add broccoli noodles, season with salt, and cook for about 3 minutes. Add blanched florets and cook until hot, then add the thickened marinade and toss to coat.
Divide the noodles between 2 plates. Top with sliced steaks and serve.