Preheat the oven to 400°F (200°C).
Line a baking sheet with parchment paper.
Place the salmon fillets skin-side down on the prepared baking sheet.
Using a sharp knife, carefully slice down the center of each fillet lengthwise to create a pocket. Avoid cutting all the way through.
Brush the salmon with 1 tablespoon olive oil and season with salt and pepper.
Heat the remaining olive oil in a large skillet over medium heat.
Add spinach, Italian seasoning, paprika, cayenne pepper, salt, and pepper.
Cook for 2–3 minutes until the spinach wilts.
Remove from heat.
Stir in feta cheese, parmesan cheese, and chopped roasted red peppers.
Mix thoroughly, gently mashing the feta until the filling becomes creamy and cohesive.
Spoon the spinach and feta mixture evenly into each salmon pocket.
Bake the Stuffed Salmon with Spinach & Feta for 12–17 minutes, depending on thickness and preferred doneness.
Remove from the oven and serve immediately