Preheat oven to 350 degrees Fahrenheit. Lightly grease an 8x8" baking dish. In the bowl of an electric mixer, pour HALF the package of yellow cake mix (split the mix in half with your hand on the outside of the bag (see blog post for a picture example), then pour). Don't bother measuring.

Add one large egg and 1/4 c. softened butter to the bowl and mix until incorporated. Scrape batter out well with a spatula and spread into the prepared pan.

Use the same bowl for the pumpkin layer. Don't bother to wash it. Pour the remaining half package of yellow cake mix into the mixing bowl. Add one large egg, 1/4 c. pumpkin puree, 2 Tbsp. softened butter, and 1 tsp. pumpkin pie spice and mix until incorporated. Spread over the yellow layer and bake for approximately 22-25 minutes, or just until set. Let cool slightly, then slice and serve, warm, with a dollop of whipped topping or whipped cream on top of each piece.