reheat oven 350°F. Coat baking dish with nonstick cooking spray.
In bowl, combine cream cheese and feta with fork, mixing until blended. Add onion and spinach, combining well.
Split each piece of salmon in half lengthwise without cutting all the way through (make pocket). Divide filling in each fillet spreading to cover. Place top salmon piece back over filling and on prepared baking dish. Bake 20 minutes or until flaky and done.
Recipe Notes
Stuff the salmon ahead of time and refrigerate until ready to cook.