Preheat the oven to 375°F (190°C). Line a baking sheet with parchment paper.

In a medium skillet, heat olive oil over medium heat. Add minced garlic and sauté for about 30 seconds, until fragrant.

Stir in the chopped spinach and cook until wilted, about 2-3 minutes. Remove from heat and let cool slightly.

In a bowl, combine the cooked spinach, cream cheese, feta cheese, breadcrumbs, lemon juice, salt, black pepper, and red pepper flakes. Mix until well combined.

Place the salmon fillets skin-side down on the prepared baking sheet. Using a sharp knife, make a pocket in each fillet by slicing horizontally, being careful not to cut all the way through.

Stuff each salmon pocket generously with the spinach mixture, packing it in snugly.

Bake in the preheated oven for 15-20 minutes, or until the salmon is cooked through and flakes easily with a fork.

Garnish with chopped parsley before serving. Enjoy your spinach stuffed salmon with a side of steamed vegetables or a fresh salad.