Preheat your oven to 350°F (175°C) and grease a 9x13-inch baking pan.
Whisk together flour, sugar, baking powder, cinnamon, and salt in a large mixing bowl.
In another bowl, mix pumpkin puree, eggs, buttermilk, and vanilla extract until smooth.
Combine the wet mixture with the dry ingredients and stir until just combined.
Spread the batter evenly in the prepared pan and bake for 25-30 minutes or until a toothpick comes out clean.
Let the cake cool for about 10 minutes before poking holes all over it with a fork. Pour warm caramel sauce over the cake to allow it to seep in.
Allow to cool completely before topping with whipped cream. Chill for an hour before serving.