Pre-heat oven to 375 degrees
Start by combing Flour, salt, baking soda, baking powder, and Pumpkin Spice in a bowl. Use a whisk to mix well together.
In a seperate bowl, add in 3 eggs and 1 cup of granulated sugar. Use a mixer to mix until thick.
Add in Pumpkin Puree and mix until well combined
Add in half of the flour mixture to the egg, sugar, and pumpkin mixture. Mix until all the flour mixture is combine then add in the other half and mix that in.
Next, grease a 15 x 10 jelly roll pan and then add parchment paper to the top. I also like to grease the top of the parchment paper as well.
Pour your mixture onto the jelly roll pan and spread evenly. You can also hit the pan on your counter top to help make the mixture even and to pop any bubbles.
Bake in oven for 12 to 15 minutes, until cake is spongie in the middle and a tooth pick comes out clean.
Flip cake out onto a cooling rack. I like to put a towel down first so the cake won't settle into the groves of the drying rack.
Next, peel off the parchment paper from the cake.
Allow cake to completely cool. After cake has cooled, spread on cream cheese icing and then sprinkle with walnuts. You can then cut into even squares.