Prepare a tube pan with a parchment round. Grease the pan and the paper and then sprinkle with sugar. Set aside. Preheat oven to 325°F.
Fan the sliced pears around the bottom of the pan.
Whisk together the flours, baking soda, cinnamon, nutmeg and salt in a bowl, set aside. In a stand mixer combine the oil, sugars, vanilla, Calvados and eggs. Add the dry ingredients and mix until well combined. Add the apples and nuts. Pour into the prepared pan, over the pears.
Bake for about 1 hour and 25 minutes in the center of the oven, until a tester comes out clean. Allow the cake to cool for about 20 minutes before removing from the pan.
Carefully invert the cake onto a cake plate. Use one that has a slight lip to it to catch the caramel sauce.
In a small sauce pot combine all the ingredients for the caramel and bring to a gentle boil for 2-3 minutes. Allow the glaze to cool slightly, to thicken it, and pour over the top of the cake.
Serve with ice cream, a dollop of whipped cream or a cup of coffee.