Preheat oven to 350 degrees F.
Cut 1 loaf pumpkin bread into 1/2-1 inch cubes. Spread out on a baking sheet and toast for 25 minutes at 350 degrees F. Stir bread and continue to toast an additional 10 minutes or until dried out like croutons.
Meanwhile, whisk the eggs together in a medium bowl. Stir in all remaining Pumpkin Bread Pudding ingredients EXCEPT BUTTER until evenly combined.
Evenly layer toasted pumpkin bread cubes in a greased 9 by 13-inch baking dish. Pour the pumpkin mixture over the bread, pressing down on the bread to totally submerge it. Let sit for 15 minutes. Sprinkle cubed butter over top.
Bake at 350 degrees F for approximately 60 minutes or until a knife inserted in the center comes out clean (the center will still be slightly jiggly). Cool on a baking rack for at least 30 minutes before serving.
Caramel Sauce: Just before serving, melt 1/2 cup butter over medium high heat in a small saucepan. Add 1/2 cup packed brown sugar and 1/4 cup heavy cream, whisking until sugar dissolves and sauce is heated through. Remove from heat and stir in vanilla. You can make ahead and reheat when ready to serve but you might need to add a little extra heavy cream as sauce thickens upon standing.
Serve warm Caramel Sauce with Pumpkin Bread Pudding.