01 -
Preheat oven to 325°F and grease an 8x8 inch pan with baking spray. Line the bottom with parchment paper. Set aside.
02 -
In a large saucepan, combine water and raisins. Bring to a gentle boil and cook for 10 minutes. Add vegetable oil to the boiled mixture, then allow it to cool to room temperature.
03 -
In a separate bowl, combine flour, sugar, pumpkin pie spice, baking soda, and salt. Whisk to break up any lumps.
04 -
Mix the dry ingredients into the cooled raisin mixture. Add the beaten egg and walnuts, if using, and stir until combined.
05 -
Pour the batter into the prepared pan and bake for 35-40 minutes, or until a toothpick inserted comes out mostly clean with a few moist crumbs. Cool completely before assembling.
06 -
In a large bowl, beat cream cheese and butter until smooth and lump-free, about 2 to 3 minutes. Gradually add powdered sugar and salt, beating until smooth.
07 -
Remove the cooled cake from the baking pan and place it on a cutting board. Slice the cake in half. Transfer one layer to a serving tray and apply frosting on top. Top with the second layer and frost the top and sides. For a grooved pattern, use a fork to draw lines in the frosting.