Preheat oven to 350F. Put the spinach into a pan with a little of water, cover and bring to boil and cook for two minutes, then drain and refresh under cold water. Squeeze spinach dry. Place spinach, egg yolks, basil, salt and pepper into a food processor. Pulse to a smooth paste. Whisk egg whites until they hold soft peaks then fold into the basil-spinach mixture. Spread this mixture on a baking tray lined with buttered parchment and bake for 15 minutes or until set.Turn baked roulade out onto another sheet of parchment and leave to cool.
For the filling combine cream cheese, dill, lemon zest and juice. Season with salt and pepper to taste. Place the spinach roulade onto a piece of plastic wrap. Spread the filling evenly over the spinach leaving a side border of 1 cm. Sprinkle with capers, more dill if you like and black pepper. Cover the filling with the salmon slices. Roll up with the help of the plastic wrap. Twist the ends to secure.Refrigerate for few hours or overnight.