Remove steaks from refrigerator 30 minutes before cooking. Pat dry with paper towels and season both sides with salt and pepper.
Preheat grill to high heat (about 450-500°F). Brush grill grates with oil.
Grill steaks for 4-5 minutes per side for medium-rare, or to desired doneness. Transfer to a cutting board and let rest for 5 minutes.
While steaks rest, in a small saucepan over medium-high heat, add Merlot and beef broth. Bring to a boil and cook until reduced by half, about 5-7 minutes.
Reduce heat to low and whisk in cold butter pieces one at a time until melted and sauce is smooth. Stir in thyme.
Serve steaks with sauce drizzled on top.
Tips
For a non-alcoholic version, substitute Merlot with equal parts grape juice and balsamic vinegar.
Letting the steak rest is crucial for juiciness.
Leftover sauce can be stored in the refrigerator for up to 3 days.