Preheat your oven to 350°F (175°C).
Place the sliced pears into a large mixing bowl. Add the granulated sugar, cinnamon, nutmeg, and ginger, tossing the fruit gently until each piece is evenly coated with the spices.
Transfer the seasoned pear mixture into the bottom of the 9×13 inch baking dish, spreading them out into an even layer.
Sprinkle the dry yellow cake mix directly over the pears, using a spatula to gently level it out without packing it down.
Scatter the chopped walnuts evenly over the top of the dry cake mix layer.
Distribute the thin slices of butter across the entire surface, ensuring the butter is spread out so it covers as much of the dry mix as possible.
Bake for 40 to 45 minutes, or until the top is golden brown and the fruit juices are bubbling vigorously around the edges of the dish.
Remove from the oven and allow the dessert to stand for 10 minutes before serving, which helps the juices thicken slightly.