Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.
In a small pan, heat 1 tablespoon of olive oil over medium heat and sauté the spinach until just wilted. Drain any excess liquid.
In a bowl, combine the wilted spinach, feta, parmesan, and roasted red peppers.
Using a sharp knife, cut a pocket into the thickest part of each salmon fillet, being careful not to cut all the way through.
Stuff each pocket generously with the spinach and cheese mixture.
Rub the outer salmon fillets with the remaining olive oil, then season with Italian seasoning, paprika, cayenne pepper, salt, and pepper.
Place the fillets on the prepared baking sheet and roast for 15-20 minutes, or until the salmon flakes easily with a fork and the filling is heated through.