This bar tastes just like pecan pie, but an assortment of your favorite snack nuts takes the place of the pecans.
Preheat oven to 350 degrees F. Line a 13x9x2-inch baking pan with foil, extending foil over edges of pan. Coat foil with cooking spray; set aside.
Place cake mix in a large bowl. Using a pastry blender, cut the 1/2 cup butter into cake mix until mixture resembles coarse crumbs. Press mixture evenly onto the bottom of the prepared pan. Bake for 15 to 20 minutes or until lightly browned and set.
Meanwhile, in a large bowl whisk together eggs, brown sugar, corn syrup, the 1/3 cup melted butter, the vanilla, and cinnamon. Stir in mixed nuts. Pour nut mixture over warm crust. Bake about 30 minutes more or until bubbly around the edges and golden brown.
Cool in pan on a wire rack. Using the edges of the foil, lift uncut bars out of pan. Cut into bars.
Layer bars between sheets of waxed paper in an airtight container; cover. Store in the refrigerator for up to 1 week or freeze for up to 3 months.