Preheat oven to 350°F.

Butter 15x10x1-inch baking pan and line the pan with wax paper; buttering the paper as well.

In a large mixing bowl, mix granulated sugar, flour, baking powder, 2 teaspoons of the pumpkin pie spice and salt. Stir in eggs and pumpkin until well blended and smooth. Spread evenly in prepared pan.

Bake 15 to 20 minutes or until toothpick test in center comes out clean.

Place clean kitchen towel on work surface; dust with 2 tablespoons confectioners' sugar. Loosen cake around sides of pan with small knife. Turn out onto sugared towel, wax paper-side up.

Fold 1 side of towel over short side of cake, then roll up cake jelly-roll style. Cool cake completely.

In a large mixing bowl; mix cream cheese, 1 cup confectioners' sugar, butter, vanilla and remaining 3/4 teaspoon pumpkin pie spice until well blended and smooth. Add walnuts if desirec.

Unroll cake onto towel. Peel off wax paper. Spread cream cheese mixture evenly over cake. Using towel, roll up cake and place seam-side down on serving platter. Trim ends of cake.

Refrigerate 1 hour or until ready to serve. Sprinkle cake with additional confectioners' sugar just before serving.