Preheat oven to 375°. Line a rimmed baking sheet with parchment paper.
In a medium bowl, combine cream cheese and feta, mixing until smooth. Add scallion, spinach and lemon juice; mix well. Spread 1/4 of the mixture over each salmon fillet.
Unroll phyllo sheets onto a smooth, dry surface and cover with a damp towel. Working quickly, lay one phyllo sheet on counter, brush with melted butter and top with another sheet of phyllo. Brush second sheet lightly with melted butter. Lay one salmon fillet at the short end of the phyllo and roll, tucking sides in. Place package, seam side down (cheese covered side of salmon up), on parchment lined pan. Brush with melted butter. Repeat with remaining salmon. Bake for 30-35 minutes until browned. Serve with Lemon Aioli (Sauces Chapter).
Leigh's tip: Prepare early in the day and refrigerate until ready to bake. These freeze well before baking. Place frozen on parchment lined pan and bake in preheated 400° oven 30-35 minutes, until golden brown and cooked through.