Preheat your oven to 350°F (175°C) and prepare an 8-inch round cake pan by greasing it with butter or cooking spray and dusting it lightly with flour.

In a medium mixing bowl, whisk together the all-purpose flour, baking powder, baking soda, cinnamon, nutmeg, and salt until well combined.

In a large mixing bowl, cream the softened unsalted butter and granulated sugar together with an electric mixer until light and fluffy, then add eggs one at a time, mixing well after each addition, followed by vanilla extract.

Gradually alternate adding the dry flour mixture with the buttermilk into the creamed butter mixture, mixing on low speed just until combined.

Gently fold in the caramel sauce using a spatula, ensuring it is evenly incorporated.

Pour the batter into the prepared cake pan and smooth the top, then bake for 30 to 35 minutes, or until a toothpick comes out clean.

Let the cake cool in the pan for about 10 minutes, run a knife around the edges, and invert it onto a wire rack to cool completely.

While the cake cools, whisk together powdered sugar and milk until smooth to prepare the glaze.

Once cooled, drizzle the glaze over the cake, allowing it to flow down the sides, and optionally drizzle more caramel on top.