Preheat oven to 350°F (175°C). Grease a 9x13-inch baking pan with nonstick baking spray.

In a large mixing bowl, beat together the spice cake mix, pure pumpkin puree, whole milk, vegetable oil, eggs, pumpkin pie spice, and vanilla extract on medium speed for 2 minutes until thick and smooth.

Spread batter evenly into the prepared pan. Bake for 28 to 32 minutes, or until a wooden toothpick inserted into the center comes out clean.

While the cake is still warm (about 5 minutes out of the oven), use the round handle of a wooden spoon to poke holes evenly across the entire surface of the cake, spaced about 1 inch apart and going about three-quarters of the way down.

Whisk the sweetened condensed milk with 1/2 cup of warmed caramel sauce. Slowly pour the sweet mixture over the warm cake, making sure it fills all of the poked holes.

Allow the cake to cool to room temperature on the counter for 30 minutes, then cover and transfer to the refrigerator to chill for at least 2 hours (or overnight) so the soak absorbs completely into the crumb.

Before serving, spread whipped topping evenly over the chilled cake. Drizzle with remaining caramel sauce, sprinkle with toasted chopped pecans, and dust lightly with cinnamon. Slice into squares and serve cold!