Brush one sheet of filo dough with melted butter and place one of the salmon fillets towards the edge of the sheet so that it can be properly rolled later.
Season the salmon with the salt, pepper, and lime juice.
Spread a bit of crème fraîche over the seasoned salmon fillet, followed by the spinach. Finally, sprinkle the nutmeg on top of the spinach.
Pull the sides of the dough in to cover the salmon, but before you roll, brush the entire dough area with egg. Now tuck in the edges and tightly roll.
Gently score the dough 2-3 times before baking for 15 minutes at 375°F.