Preheat oven to 350 degrees. Line quarter sheet pan with parchment paper, making sure paper extends over the side. This makes it easier to lift the cake from the pan, when finished.

In a small bowl, combine flour, salt, baking powder and spices. Set aside. 

In a large bowl or stand mixer, combine egg, egg white, and sugar. Mix on high for 5 minutes. This may seem like a long time, but we want the eggs to be aerated to help make a lighter cake. It should be a pale yellow color. 

Whisk in the pumpkin and lemon juice.

After egg and pumpkin mixture is whipped, turn off mixer and fold the dry ingredients into the egg and sugar mixture. Folding in the flour prevents deflating the eggs we just whipped. This may take a few minutes to incorporate all the flour. 

Spread batter into lined quarter sheet pan and bake for 15 minutes. 

While cake is baking, heavily dust a tea towel with powdered sugar. Make sure the towel you choose is larger than the cake pan. 

Once cake is done baking, remove from oven and allow to set for 2-3 minutes. No longer than that. Then, invert onto dusted tea towel. Gently pull up parchment paper from the cake, and dust bottom of cake with powdered sugar. 

Beginning at the short end of the cake, roll the cake with the towel inside it. The towel prevents the cake from sticking to itself, and the powdered sugar prevents the cake from sticking to the towel. 

Allow the cake to cool for one hour or longer. Meanwhile, set out cream cheese and butter, so they will be at room temperature when you are ready to fill the pumpkin roll. 

After cake has cooled, prepare the frosting. Start by whipping the room temperature cream cheese and butter at least 2 minutes. We want it to be creamy. Then, add vanilla and nutmeg. Finally, slowly add sifted powdered sugar. (Make sure it is sifted, or you'll have clumps in your frosting.) 

Gently unroll cooled cake and spread frosting the length of the cake. 

Once filled, gently reroll cake. (No towel inside this time!) Roll the filled cake starting with the same side you rolled for cooling the cake. 

Place the rolled cake in the fridge and allow to chill 2-3 hours prior to serving. 

Dust with additional powdered sugar, if desired.