Preheat your oven to 375°F (190°C). Line a baking sheet with parchment paper or foil.
Prepare the Salmon:
Pat the salmon fillets dry with paper towels. Using a sharp knife, cut a pocket into the side of each fillet, being careful not to cut all the way through. Season the fillets with garlic powder, paprika, salt, and black pepper.
Make the Filling:
In a medium bowl, mix together the chopped spinach, softened cream cheese, Parmesan cheese, breadcrumbs, minced garlic, and red pepper flakes (if using).
Stuff the Salmon:
Divide the filling evenly and stuff each salmon fillet pocket with the spinach mixture. Use toothpicks if necessary to secure the filling.
Sear the Salmon:
Heat the olive oil in a large oven-safe skillet over medium-high heat. Sear the stuffed salmon fillets for 2-3 minutes on each side, until golden brown.
Bake:
Transfer the skillet to the preheated oven and bake for 10-12 minutes, or until the salmon is cooked through and flakes easily with a fork.
Serve:
Remove the toothpicks (if used) and serve the stuffed salmon warm. Garnish with fresh parsley or lemon wedges, if desired.