Prepare the Mustard-Horseradish Butter: In a small bowl, combine the softened butter, Dijon mustard, and prepared horseradish. Mix until well blended. Season with salt and pepper to taste. Set aside at room temperature.

Prepare the Ribeye Steaks: Preheat your grill or a skillet over medium-high heat. Pat the ribeye steaks dry with paper towels. In a small bowl, mix the toasted dill seeds, Meyer lemon zest, salt, and pepper. Rub the olive oil over the steaks, then press the dill and lemon zest mixture onto both sides of each ribeye, ensuring they are well-coated.

Cook the Ribeye Steaks: Place the ribeye steaks on the hot grill or skillet. Cook for about 4-5 minutes on each side for medium-rare, or until your desired doneness is reached. Use a meat thermometer to check the internal temperature; it should read 130°F (54°C) for medium-rare.

Rest the Steaks: Once cooked to your liking, remove the steaks from the heat and let them rest for 5-10 minutes. This allows the juices to redistribute throughout the meat.

Serve: Slice the ribeye steaks against the grain and serve on plates. Top each steak with a generous dollop of the mustard-horseradish butter. Garnish with additional dill or lemon zest if desired.