Start by slicing the top sirloin steak against the grain into thin strips. Season with kosher salt and black pepper.
In a large skillet or wok, heat the vegetable oil over medium-high heat, then add the steak strips in a single layer.
Cook the steak for about 2-3 minutes on each side until browned and cooked to your desired doneness. Remove and set aside.
Add the unsalted butter to the skillet. Once melted, toss in the sliced onion and minced garlic and sauté for about 2-3 minutes.
Add the broccoli florets to the skillet and stir-fry for about 4-5 minutes until bright green and tender but crisp.
Return the cooked steak to the skillet and add lemon juice, Worcestershire sauce, beef bouillon, thyme, oregano, and red pepper flakes. Stir for 2 minutes.
Serve the steak and broccoli mixture over cooked white rice. Enjoy!