01 -
Turn your oven on to 350°F (175°C). Grease a 9×9-inch (23×23 cm) baking pan and dust with flour, or just line it with some parchment paper.
02 -
Grab a medium bowl and stir together the flour, sugar, baking powder, baking soda, and salt. In another bigger bowl, beat your softened butter with the egg until it's fluffy. Pour in the coffee, buttermilk, and vanilla, then mix it all up. Slowly add your dry mix to the wet stuff and stir until it's smooth.
03 -
Dump the batter into your pan and stick it in the middle of your hot oven for about 25-30 minutes. You'll know it's done when you poke it with a toothpick and nothing sticks. Let it sit in the pan for 10 minutes before moving it to a wire rack to cool off completely.
04 -
Put the brown sugar, butter, and heavy cream in a pot over medium heat. Keep stirring until you see bubbles. Let it bubble for 3-4 minutes while stirring now and then until it gets a bit thick. Take it off the heat and mix in the vanilla and small pinch of salt. Let it cool down a little.