Preheat the oven to 375°F.
Grate the pumpkin using the large side of a box grater.
Heat 2 tablespoons oil or butter in a large skillet over medium heat. Add the grated pumpkin and cook for about 5 to 7 minutes to remove excess moisture.
Stir in the sugar, walnuts, cinnamon, and nutmeg if using. Remove from heat and allow the filling to cool slightly.
Lay one sheet of filo dough on a clean surface and lightly brush with melted butter or oil. Place another sheet on top.
Spread a thin layer of pumpkin filling along one edge of the filo.
Roll tightly into a long log.
Repeat with remaining filo and filling.
Arrange the rolls in a greased baking dish either straight or coiled into a spiral.
Brush the tops generously with melted butter or oil.
Bake for 35 to 45 minutes or until deeply golden and crispy.
Allow the Tikvenik to cool slightly before slicing.
Dust with powdered sugar before serving.