Preheat oven to 350° F and prepare a 9" x 13" dish with cooking spray. Mix pumpkin, sugars, and spice in a large bowl. Add beaten eggs and evaporated milk and stir to incorporate.
Pour pumpkin mixture into the prepared pan. Whisk cake mix in a medium bowl to break up any lumps. Sprinkle evenly over the pumpkin.
Sprinkle pecans (optional) and then butter over the cake mix.
Bake for 1 hour, 15-20 minutes. Cobbler is finished when the top is golden brown and the cake mix no longer looks crumbly.
Divide into bowls and serve warm, topped with whipped cream or vanilla ice cream and a sprinkling of cinnamon.