Creating the delectable Pumpkin Apple Cake can be straightforward if you follow these easy steps:

1. Preheat your oven to 350°F (175°C). Grease and flour a 9×13-inch cake pan.
2. Mix Dry Ingredients: In a medium bowl, whisk together the flour, baking powder, baking soda, cinnamon, nutmeg, and salt.
3. Combine Sugars and Oil: In a large bowl, mix the granulated sugar, brown sugar, and vegetable oil until well combined.
4. Add Eggs and Pumpkin: Beat in the eggs one at a time, then add the pumpkin puree and vanilla extract. Mix until smooth.
5. Combine Mixtures: Gradually add the dry ingredients to the wet ingredients, stirring until just combined. Do not overmix.
6. Fold in Apples and Nuts: Gently fold in the diced apples and walnuts or pecans if using.
7. Pour Batter: Pour the batter into the prepared cake pan, spreading it evenly.
8. Bake: Place in the preheated oven and bake for 40-45 minutes or until a toothpick inserted in the center comes out clean.
9. Cool: Remove from the oven and allow the cake to cool in the pan for 15-20 minutes. Then transfer it to a wire rack to cool completely.
10. Dust with Powdered Sugar: Once the cake is cool, dust the top with powdered sugar for an elegant touch before serving.

These steps will guide you in creating a delightful Pumpkin Apple Cake that is sure to impress everyone!