Rinse the meat and pat dry with a kitchen towel. Place on a clean work surface and slice into half-inch thick slices. Set aside.

Whisk together oil, crushed garlic, dried rosemary, lemon zest, and orange zest. Brush the meat with this mixture and refrigerate for 30 minutes.

Preheat a large grill pan or an electric grill to medium-high heat. Remove the meat from the refrigerator and grill for 6-7 minutes on each side.

When done, generously brush with butter.

Serve with some low-carb salad or veggies