Remove your salmon 30 minutes prior to baking so that it comes to room temperature.
Preheat oven to 420°F. Line a medium baking tray with parchment paper.
Rinse and pat dry your salmon filets. Take a small sharp knife and cut a slit into the thick part of the side of each fillet. The cut should go as deep as possible without slicing through to the other side.
In a deep skillet, heat 1 tbs olive oil on medium high and cook your scallions for a minute or two. Stir in the garlic for 15 seconds. Add the spinach, dill, season with salt and pepper to taste, and sauté until the spinach is mostly wilted but not entirely. Remove mixture from your pan promptly and transfer to a bowl. Wait 5 minutes and then mix in your crumbled feta.
Stuff the salmon with the mixture and carefully place the fillets back up right. Brush the tops and sides with olive oil and season with salt and pepper to taste. Sprinkle top and sides of fish with the paprika (this gives it a nice color) Bake for about 17 minutes (cook times vary with the size of your fish).