In a medium bowl, combine chopped spinach, softened cream cheese, grated Parmesan, chopped roasted red peppers, minced garlic, lemon juice, salt, and black pepper. Mix well until creamy and smooth.
Place the salmon fillets skin-side down on a clean cutting board. Carefully cut a pocket into each fillet without cutting all the way through.
Spoon the creamy spinach mixture into each salmon fillet pocket, using your fingers or a spoon to gently press the filling in.
Heat olive oil in a large oven-safe skillet over medium-high heat. Add the stuffed salmon fillets skin-side down and sear for about 3-4 minutes until the skin is crispy.
Carefully flip the fillets and transfer the skillet to the preheated oven. Bake for 10-12 minutes or until the salmon is cooked through and flakes easily with a fork.
Remove the skillet from the oven and let the fillets rest for a few minutes. Garnish with fresh parsley before serving.