• Preheat the oven to 350℉/180℃. Grease an 8×8 inch square pan. For easy removal of the cake, place parchment paper on the bottom and 2 sides of the pan. Grease again and then set side.
• Before starting, spread the pumpkin puree onto a plate and blot it with paper towel sheets to remove any excess liquid. Do this twice and set aside.

For the pumpkin cake

• In a large bowl, mix the flour, light brown and white sugar, and butter in a large bowl. Using your hands or a fork, mix until a crumbly mixture forms. Measure out 3/4 cups of this mixture and set aside. This will be the streusel topping for later.
  1/2 cup butter, 1 3/4 cups all-purpose flour, 1/2 cup dark brown sugar, 1/3 cup white sugar
• With the remaining crumble mixture, add in the pumpkin puree, sour cream, eggs, and vanilla. Using a whisk, mix until smooth.
  1 cup pumpkin puree, 2 eggs, 1/3 cup sour cream, 1/2 tsp vanilla
• Add in the corn starch, cinnamon, allspice, ginger, nutmeg, baking soda, baking powder, and salt. Using a spatula, fold until a soft batter forms. Do not overmix!
  1 1/2 tsp corn starch, 3/4 tsp baking soda, 3/4 tsp baking powder, 1/4 tsp ground ginger, 1/4 tsp allspice, 1/8 tsp nutmeg, 1 tsp cinnamon

For the apples

• In a medium sized bowl, add in the cinnamon, cornstarch, brown sugar, cubed apples, and hot butter.
  3 tbsp butter, 1 tsp cinnamon, 3 tbsp dark brown sugar, 2 large granny smith apples, 1 tsp cornstarch
• Mix with a fork until the apples are completely covered.
• Time to layer the cake! Add the pumpkin cake layer into the prepared 8x8 pan and spread evenly. Sprinkle the apples. Add the streusel, and finish of with sprinkling the chopped walnuts.
  1/2 cup walnuts
• Bake the bars for 55 minutes to 1 hour. A toothpick inserted will come out with moist crumbs. Once ready, slightly open your oven door to allow the hot air to come out. If you remove your cake from the oven right away, it will drop.
• After 10 minutes, remove from the oven completely and set on your counter to cool. Allow the cake to cool completely before slicing into them. Enjoy!
• This cake is best eaten within 2 to 3 days of being baked!