Preheat your oven to 375°F (190°C). In a mixing bowl, combine fresh spinach and crumbled feta cheese until well mixed. Set aside.

Lay the salmon fillet skin-side down on a cutting board. Carefully slice it to create a thin, flat piece, about half an inch thick. Season with salt and pepper.

Spread the spinach and feta mixture evenly over the salmon. Roll the salmon tightly into a log shape and secure with toothpicks or kitchen twine.

Place the rolled salmon pinwheels seam-side down in a greased baking dish. Brush the tops with olive oil and bake for 15-18 minutes.

Let the pinwheels rest for a couple of minutes. Remove toothpicks or twine, slice, and garnish with dill or lemon before serving.