Sauté fresh spinach in a pan with a drop of olive oil for 2 minutes until wilted. Let cool and squeeze out all excess liquid using paper towels. In a bowl, combine the squeezed spinach, Greek yogurt, crumbled feta, grated Parmesan, minced garlic, lemon zest, salt, and pepper.

Lay salmon fillets flat on a cutting board and pat completely dry. Using a sharp knife, slice a horizontal pocket into the side of each fillet, leaving a 1/2-inch border along the edges.

In a small bowl, mix smoked paprika, garlic powder, onion powder, cumin, salt, and black pepper. Rub spices generously over the outside of all fillets. Spoon 2 to 3 tablespoons of filling into each pocket.

Heat extra virgin olive oil in a cast-iron skillet over medium-high heat. Place stuffed salmon in the hot pan and cook undisturbed for 4 to 5 minutes until a deep crust forms.

Carefully flip with a fish spatula, reduce heat to medium, and cook for another 4 to 5 minutes until cooked through and cheese is melty. Serve warm with lemon wedges.