Preheat the oven to 325 degrees. Spray a 10-cup bundt pan with cooking spray, sprinkle in some flour, and coat the bottom and sides well, tapping out the excess.
Cream the butter and sugars together in a mixer, preferably fitted with a paddle attachment, on medium-high speed. Add the eggs, one at a time, beating well after each addition. Beat in the vanilla.
In a mixing bowl, whisk together the flour, baking powder, baking soda, and salt. Turn the mixer to low, add half the flour mixture, the sour cream, and finally the rest of the flour mixture. Scrape the bottom and sides of the bowl well to make sure all ingredients are fully combined. Save a handful of the toffee bits for garnish and fold the rest into the batter. Pour the batter into the prepared pan and bake for 60 – 70 minutes or until the cake springs back when touched lightly and a toothpick inserted into the center comes out clean.
Let cool completely in the pan.
Heat the caramel sauce slightly and mix with enough powdered sugar to make a glaze.
Invert the cake onto a cake plate or stand. Drizzle with the caramel sauce, top with the reserved toffee bits, and serve.