Ingredients

For the pecan pie filling:
Nonstick cooking spray
2 cups pecan pieces
1/2 cup (107 g) brown sugar
1 cup (312 g) light corn syrup
1/4 cup evaporated milk
4 large eggs
1 teaspoon vanilla flavoring or extract
1 stick (4 ounces or 113 g) unsalted butter, melted
1/4 teaspoon salt

For the crumble topping:
1 (15.25-ounce) box yellow cake mix (like Duncan Hines)
1 stick (4 ounces or 113 g) unsalted butter, melted
1/2 cup pecan pieces

Directions

Preheat the oven to 350°F.

Position a rack in the center of the oven. Spray a glass 9×13-inch baking dish with cooking spray.
Make the pecan mixture:

Scatter the pecan pieces in the bottom of the prepared baking dish.

In a large mixing bowl whisk to combine the brown sugar, corn syrup, evaporated milk, eggs, vanilla, melted butter, and salt. Whisk until the mixture is homogeneous and the sugar is mostly dissolved, about 2 minutes.

Slowly pour the mixture over the pecans in the baking dish. Some pecan pieces will rise to the top.
Make the topping:

In a large bowl, combine the cake mix and melted butter and mix with a fork until a crumbly texture forms. Use your hands to sprinkle this crumble evenly over the pecan pie mixture. Sprinkle the pecans over the crumble.
Bake the cake:

Bake until the edges of the crumble start to turn golden brown, 35 to 40 minutes.

Allow to cool for 5 minutes, then serve warm with vanilla ice cream or whipped cream.

Refrigerate leftovers in an airtight container for up to 3 days. Reheat in the microwave for about 10 seconds before enjoying.