Combine softened butter and miso paste in a small bowl.

Add sliced green onions and black pepper to the butter mixture.

Mix well to create the miso butter.

Shape the miso butter into a log using plastic wrap and refrigerate, or keep at room temperature.

Preheat oven to 275°F (135°C) with a cast-iron skillet inside.

Place a wire rack on a rimmed baking sheet.

Pat ribeye steaks dry with paper towels to remove excess moisture.

Season both sides of the steaks generously with kosher salt and black pepper.

Place seasoned steaks on the wire rack and transfer to the preheated oven.

Cook the steaks in the oven for 15-20 minutes, until the internal temperature reaches 90-95°F (32-35°C) for medium-rare or 100-105°F (38-41°C) for medium.

Remove the steaks from the oven.

Heat vegetable oil in the warmed cast-iron skillet over high heat until it begins to smoke.

Carefully add the steaks to the hot skillet and sear for about 2 minutes, until a brown crust forms.

Flip the steaks and sear the other side for 1 1/2-2 minutes, until the internal temperature reaches 120-125°F (49-52°C) for medium-rare or 130°F (54°C) for medium.

Reduce the heat to medium and add unsalted butter, roughly chopped garlic, and sliced white and light green parts of green onion to the skillet.

Turn the steaks onto their sides to cook and render any remaining fat, for about 1-2 minutes.

Baste the steaks with the butter, garlic, and green onion mixture.

Remove the steaks from the skillet and transfer them to a clean wire rack set on a sheet pan.

Let the steaks rest for 10 minutes.

Slice the miso butter into rounds.

Top the rested steaks with the miso butter slices, sliced green onions, and cilantro leaves.

Serve immediately.