Remove the Porterhouse (T-bone) Steak from the refrigerator at least 45–60 minutes before cooking so it comes to room temperature; pat dry with paper towels.
Preheat a grill or a heavy cast-iron skillet until extremely hot and smoking. Brush both sides of the steak with Extra-Virgin Olive Oil, then season generously with Coarse Sea Salt and freshly cracked Black Pepper.
Lightly bruise a few sprigs of Rosemary with the flat of a knife to release the oils; you can tuck a sprig on the steak while it rests or toss one on the coals/pan briefly to perfume the meat.
Place the steak on the hot grill or skillet and sear without moving it for about 4–6 minutes per side for a 1.5–2 inch thick steak (adjust time for thickness). Aim for a well-charred crust and an internal temperature of about 125–130°F (52–54°C) for rare to rare-medium, the traditional doneness for Florentine steak.
Once both sides are seared (and you’ve also seared the bone-facing edges for a minute each), transfer the steak to a cutting board and let it rest for 8–10 minutes so the juices redistribute. Taste and, if desired, finish with a light sprinkle more of Coarse Sea Salt.
Slice the steak across the grain into thick slices, drizzle with a little more Extra-Virgin Olive Oil, squeeze fresh Lemon over the meat to brighten the flavor, and garnish with the rested Rosemary sprigs. Serve immediately, ideally family-style so everyone can admire the charred exterior and rosy interior.
