Preheat oven to 350°F and grease a 9x13" pan.

In a large bowl, whisk together pudding mix and milk. Let sit 5 minutes until it firms up. Fold in the cake mix and stir until combined (a few lumps are ok).

Pour batter into prepared pan, smoothing the top with a spatula. Scatter the butterscotch chips and pecans on top of cake batter.

Bake cake for 35 to 40 minutes. Cake is done when it springs back when lightly pressed with your fingers. Remove from oven and let cake cool on wire rack for 30 minutes before serving.

Cake can be stored in the baking dish, covered with foil at room temperature for up to 1 week.