Pat the steak dry. Season all over with salt and pepper. Let sit while you prep.
Heat a large heavy skillet over medium-high. Add the olive oil and the potatoes, cut side down.
Cook potatoes until golden and fork-tender, 8–10 minutes, tossing a few times. Transfer to a plate.
Return the skillet to medium-high. Sear the steak 3–4 minutes per side for medium-rare, or to desired doneness.
Reduce heat to medium. Add butter, garlic, thyme, and rosemary. Tilt the pan and baste the steak for 1–2 minutes.
Move steak to a cutting board and rest 5 minutes, tenting loosely with foil.
Pour in the beef broth and lemon juice. Scrape up browned bits to make a quick pan sauce.
Return potatoes to the skillet and toss in the garlicky butter until coated and hot, 1–2 minutes. Adjust salt.
Slice the steak against the grain. Nestle into the skillet and sprinkle with parsley and red pepper flakes.
Notes
Swap sirloin with ribeye for extra richness, or add a splash of white wine when deglazing. Leftovers keep 3 days chilled; reheat gently in a skillet with a pat of butter to keep the steak tender.This recipe is an original creation inspired by classic Garlic Butter Steak and Potatoes flavors. All ingredient ratios and instructions are independently developed.