Preheat the oven to 350 degrees Fahrenheit and grease or spray a 9” x 13” baking dish with butter or cooking spray.
Transfer the avocado oil, eggs, pure vanilla extract, pumpkin puree and fresh ginger (if adding) to a large bowl. Mix the wet ingredients by hand or use an electric hand mixer.
In a separate bowl, combine the flour, brown sugar, baking powder, baking soda, ground cinnamon, pumpkin pie spice, and salt. Note: if your brown sugar is clumpy, mix it with the wet ingredients instead of the dry ingredients. If your brown sugar is fresh, however, it will mix easily with the dry ingredients.
Pour the dry ingredients into the bowl with the wet ingredients and stir until everything is combined. Transfer the cake batter into the prepared baking dish and spread into an even layer.
Bake on the center rack of the preheated oven for 30 to 35 minutes, or until the cake tests clean. A great way of determining if a cake is cooked through is by taking its internal temperature using a digital thermometer. The ideal final temperature for cake is between 190 and 205 degrees Fahrenheit.
Remove the cake from the oven and allow it to cool completely on a wire rack. To speed up the process, you can refrigerate the cake once the pan has cooled to room temperature or just above. Note that the cake must be thoroughly cooled before frosting it, or else the frosting will pull off the top layer of cake.