Preheat your oven to 350°F (175°C) and grease two 9-inch round cake pans.
In a large bowl, whisk together flour, sugar, baking powder, baking soda, salt, and pumpkin pie spice.
In another bowl, mix pumpkin puree, vegetable oil, eggs, and vanilla until well combined.
Gradually add the wet ingredients to the dry mixture, stirring until just combined.
Fold in chopped nuts if desired.
Divide the batter evenly between the prepared pans.
Bake for 30-35 minutes or until a toothpick inserted comes out clean.
Allow cakes to cool in pans for 10 minutes, then transfer to wire racks to cool completely.
Prepare cream cheese frosting while the cakes cool.
Frost the cooled cakes and decorate as desired.