Choose top sirloin steaks (about 1 to 1.5 inches thick)
Pat steak dry with paper towels
Season generously with salt and black pepper (optional: garlic powder, onion powder)
Bring steak to room temperature for 20 to 30 minutes
Preheat cast-iron skillet or heavy pan over medium-high to high heat until very hot
Add 1 to 2 tablespoons high-smoke-point oil (avocado, canola, grapeseed)
Sear steaks 3 to 5 minutes per side until deep brown crust forms
Optional: add 1 to 2 tablespoons butter, plus smashed garlic and thyme/rosemary for the last 1 to 2 minutes; tilt pan and spoon over steak
For thicker steaks, reduce heat to medium and continue cooking until done
Use a meat thermometer for doneness:
125°F / 52°C for medium-rare
135°F / 57°C for medium
145°F / 63°C for medium-well
155°F / 68°C for well-done
Transfer steaks to a plate
Rest 5 to 10 minutes
Slice against the grain
Optional finishing: brush with melted butter, squeeze fresh lemon, or add a quick pan sauce (deglaze with wine or stock, simmer, then whisk in butter)