Preheat the oven to 325°F (165°C) and prepare a 9x13-inch baking pan by greasing it and lining with parchment paper.

Sift together cake flour, baking powder, salt, cinnamon, ginger, cardamom, and nutmeg in a large mixing bowl.

Cream together the butter, brown sugar, and granulated sugar in a stand mixer until light and fluffy.

Add eggs one at a time, mixing well after each addition. Then add vanilla extract and sour cream, mixing until smooth.

Gradually add the dry ingredients to the wet mixture, alternating with buttermilk, mixing just until combined.

Pour the batter into the prepared pan and bake for 30-35 minutes until a toothpick comes out clean.

Let the cake cool in the pan for 10 minutes before transferring it to a wire rack.

For the buttercream, dissolve espresso powder in hot water and let it cool. Beat butter, powdered sugar, and heavy cream until smooth.

Stir in the cooled espresso mixture and frost the cooled cake generously with the buttercream.

Drizzle caramel sauce on top and create swirls in the frosting for decoration.