Preheat your oven to 350°F (175°C). Grease and flour a 9×9-inch baking pan.

In a large mixing bowl, whisk together the flour, sugar, baking powder, baking soda, and salt until combined.

In a separate bowl, beat the softened butter and egg together until fluffy, then stir in the brewed coffee, buttermilk, and vanilla extract.

Combine the dry ingredients with the wet mixture and mix until smooth.

Pour the prepared batter into your greased baking pan and bake for 25–30 minutes.

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

For the caramel sauce, combine brown sugar, butter, and heavy cream in a saucepan over medium heat.

Stir until simmering and thickened, then mix in vanilla extract and a pinch of salt.

Mix brewed coffee and powdered sugar until smooth for the coffee drizzle.

Poke holes in the cooled cake and pour the warm caramel sauce evenly over it.

Drizzle the coffee mixture over the top of the cake.

Slice the cake and serve it warm or at room temperature, topped with whipped cream or ice cream.