Position a rack in the lower third of the oven and preheat to 350 degrees . Butter a 3-by-6-inch round cake pan or springform pan, line with parchment and lightly butter the parchment. In a small saucepan, melt 1 stick butter over low heat and set aside.
Meanwhile, in a medium bowl, whisk together the cake flour, baking powder and 1/2 teaspoon salt. Using a hand-held electric mixer, beat the sugar and eggs at high speed until pale yellow and fluffy, about 5 minutes. At low speed, mix in half of the dry ingredients, 1/2 cup at a time. Gradually mix in the melted butter, then the remaining dry ingredients. Beat at medium speed until the batter is thick like honey, about 2 minutes. Fold in the pears and cranberries and scrape into the prepared pan, smoothing the top. Bake until a toothpick inserted in the center comes out clean, about 1 hour 10 minutes (do not open the oven door to check until at least an hour has passed). Let cool on a rack for 20 minutes, then remove the cake from the pan and let cool completely. Trim the top crust from the cake.
Make the glaze. In a small saucepan, combine the caramels, cream and remaining 1/4 teaspoon salt over medium heat. Stir occasionally until melted and smooth. Remove from the heat, then stir in the remaining 1 tablespoon butter and the whiskey. Let cool until thick but still pourable.
Invert the cake onto a plate or cardboard. Spoon the glaze on top and let it run partially down the sides.