Preheat the oven to 350 degrees F. Line a 10-inch springform pan with parchment paper and grease the sides. Set it aside.

To prepare the bottom layer, heat a skillet over low heat and sprinkle the sugar. Allow the sugar to melt on its own until it turns a golden brown color. Immediately remove the skillet from the heat, add the butter, mix, and pour the caramel over the bottom of the springform cake pan. Set it aside.

Peel the skin off the pears, remove the core, and slice them (not too thick or thin). Arrange them in a circular pattern over the caramel in the cake pan. Set them aside.

In a medium bowl, combine cake flour, baking powder, ground cinnamon, and salt. Set it aside.

In a large bowl, beat the butter, white sugar, and brown sugar using a hand mixer on medium speed for 3-5 minutes. Slowly add the eggs one after another until well combined. Add the vanilla extract and stop beating when the mixture looks pale and fluffy.

Gradually add the flour mixture in batches, alternating with the addition of milk. Mix on low speed until well combined.

Pour the prepared cake batter over the pears in the cake pan and place it in the oven. Bake for 60-70 minutes, or until a toothpick inserted in the center comes out clean.

Once done, allow the cake to cool for 15 minutes on a wire rack. Slowly release the springform pan side and remove it. Invert the cake pan upside down over a plate and remove the bottom slowly.

Slice and serve the upside-down pear cake to enjoy.