01 -
Preheat the oven to 350°F (175°C). Grease and flour a 9×9-inch baking pan or line it with parchment paper.
02 -
In a medium bowl, whisk together the flour, sugar, baking powder, baking soda, and salt. In a separate large bowl, beat the softened butter and egg until light and fluffy. Add the brewed coffee, buttermilk, and vanilla extract, and mix well. Gradually incorporate the dry ingredients into the wet mixture, stirring until a smooth batter forms.
03 -
Pour the batter into the prepared pan. Bake for 25-30 minutes or until a toothpick inserted into the center comes out clean. Let the cake cool in the pan for 10 minutes before transferring to a wire rack to cool completely.
04 -
In a saucepan over medium heat, combine the brown sugar, butter, and heavy cream. Stir constantly until the mixture reaches a simmer. Let it simmer for 3-4 minutes, stirring frequently, until thickened. Remove from heat and stir in the vanilla extract and salt. Set aside to cool slightly.