If you plan on making caramel sauce from scratch click on the recipe in the notes below and make it first so it has time to cool and thicken. You can use store bought caramel if desired.
Place the caramel in the fridge to cool down. Start by preheating your oven to 350°F. Line an 8X8 metal baking pan with parchment paper, going up and over the sides.
In a large bowl with an electric mixer, beat together 1 cup granulated sugar, 1 cup all-purpose flour, ½ cup natural cocoa powder, 1 teaspoon baking soda, ½ teaspoon baking powder, and ½ teaspoon kosher salt.
In another bowl, beat together 1 egg, 1 teaspoon vanilla extract, ¼ cup milk, ¼ cup vegetable oil, and ¼ cup room temperature sour cream.
Gradually add the wet ingredients to the dry ingredients, beating until just combined.
Pour the hot coffee into the batter and beat until fully incorporated. Do not over mix.
Pour into the pan, spreading it out evenly. Position it on the center rack of the oven to ensure even baking, avoiding placement too close to the top or bottom. Bake for 27-30 minutes or until a toothpick comes out clean. Don't open the oven door while the cake is baking.
Let cool while making the frosting.