Preheat your oven to 350°F (175°C). Lightly grease a 9-by-13-inch baking dish with butter or nonstick cooking spray. This helps prevent sticking and makes serving easier.
In a large mixing bowl, whisk together the pumpkin puree, evaporated milk, eggs, granulated sugar, cinnamon, ginger, nutmeg, cloves, salt, and vanilla extract. Continue mixing until the ingredients are evenly combined and the mixture looks smooth.
Pour the pumpkin mixture into the prepared baking dish. Use a spatula to spread it into an even layer so that the filling bakes consistently from edge to center.
Sprinkle the dry yellow cake mix evenly over the pumpkin mixture. Break up any large lumps in the cake mix before adding it. Do not stir the cake mix into the pumpkin layer; keeping the layers separate helps create the dessert's signature texture.
Slowly drizzle the melted butter over the cake mix, distributing it as evenly as possible. Try to moisten most of the surface, since dry patches may remain powdery after baking. A spoon can help spread the butter into areas that look particularly dry.
Sprinkle the chopped pecans over the top. If desired, add a little brown sugar for extra caramel-like sweetness. The pecans will toast during baking and provide a crunchy contrast to the soft pumpkin filling.
Place the baking dish on the center rack and bake for 50–60 minutes. The topping should become golden brown, and the pumpkin layer should be set around the edges with only a slight jiggle in the center. If the nuts brown too quickly, loosely cover the dish with foil toward the end of baking.
Insert a knife into the pumpkin layer near the center, avoiding the crunchy topping. The filling should be mostly set rather than liquid. If necessary, continue baking in 5-minute increments. The center will firm further as the cake cools.
Remove the dish from the oven and allow the cake to cool for at least 30–45 minutes. This resting period helps the pumpkin layer set and makes the dessert easier to portion.
Cut the Pumpkin Crunch Cake into squares and serve warm or at room temperature. Add whipped cream or a scoop of vanilla ice cream for an extra-special dessert. A light sprinkle of cinnamon makes a simple, attractive finishing touch.