Preheat your oven to 400°F (200°C) and place a heavy cast-iron skillet inside to heat up.
Pat the ribeye steak completely dry with paper towels and season both sides generously with sea salt and black pepper.
Carefully remove the hot skillet from the oven using an oven mitt, place it on the stovetop over high heat, and add the olive oil.
Sear the steak for 2 minutes on each side until a deep brown crust forms.
Transfer the skillet back into the oven and roast for 4 to 6 minutes, or until the internal temperature reaches 130°F for medium-rare.
Remove the steak from the skillet and place it on a cutting board to rest for at least 8 minutes.
While the steak rests, combine the arugula, parsley, mint, and thinly sliced radishes in a large mixing bowl.
Whisk the lemon juice and lemon zest together in a small bowl, then drizzle over the greens and toss to coat.
Slice the rested ribeye against the grain and serve immediately alongside the fresh herb salad.