Prepare the stuffing:
In a small bowl, combine the cream cheese, chopped spinach, dill, parsley, minced garlic, lemon juice, salt, and pepper. Mix until well combined. If the mixture is too thick, you can add a small amount of water or extra lemon juice to loosen it.

Prepare the salmon fillets:
Lay the salmon fillets flat on a cutting board, skin-side down. Use a sharp knife to slice each fillet horizontally, creating a pocket or flap that can be rolled up. Be careful not to slice all the way through—just create a thin opening in the center.

Stuff the salmon:
Spread a generous amount of the cream cheese mixture into the center of each salmon fillet. Gently roll the fillet up from one end to the other, securing the stuffing inside. If needed, use toothpicks to secure the edges of the roll.

Cook the salmon pinwheels:
Preheat your oven to 375°F (190°C). Place the stuffed salmon pinwheels in a lightly greased baking dish. Brush the tops of the pinwheels with olive oil to help them crisp up while baking. Bake for 20-25 minutes or until the salmon is cooked through and flakes easily with a fork.

Make the lemon butter sauce:
While the salmon is baking, melt the butter in a small saucepan over medium heat. Stir in the lemon juice, parsley, salt, and pepper. Let the sauce simmer for a few minutes, then remove from heat.

Serve:
Once the salmon is done, remove the toothpicks (if used) and transfer the pinwheels to a serving platter. Drizzle with the lemon butter sauce and garnish with extra parsley or lemon slices, if desired. Serve immediately with your choice of sides.