Preheat your oven to 350°F (175°C).
In a large mixing bowl, combine the pumpkin puree, evaporated milk, brown sugar, pumpkin pie spice, kosher salt, and eggs. Whisk until smooth.
Pour the pumpkin mixture into a greased 9x13 inch baking dish, spreading it evenly.
Sprinkle the yellow cake mix evenly over the pumpkin layer without mixing.
Sprinkle the chopped pecans over the cake mix.
Melt the unsalted butter and drizzle it evenly over the cake mix and pecans.
Bake for 50-60 minutes or until the top is golden brown and a toothpick comes out clean.
Allow to cool for a few minutes before serving.