Preheat your oven to 350°F (175°C) and prepare a 9×9-inch baking pan by greasing and dusting it with flour.

In a medium mixing bowl, whisk together the all-purpose flour, granulated sugar, baking powder, baking soda, and salt.

In a separate bowl, beat the unsalted butter and egg until light and fluffy, then mix in brewed coffee, buttermilk, and vanilla extract.

Gently fold the dry ingredients into the wet mixture using a spatula, stirring until just combined.

Pour the batter into the prepared pan and smooth the top. Bake for 25-30 minutes or until a toothpick comes out clean.

Let the cake cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.

In a saucepan, combine the brown sugar, butter, and heavy cream. Stir until the mixture thickens and bubbles.

Whisk together brewed coffee and powdered sugar until smooth to make the coffee drizzle.

Poke holes in the cooled cake and drizzle warm caramel sauce over it, followed by the coffee drizzle.

Serve the cake warm or at room temperature, optionally topped with whipped cream or ice cream.