Instructions

• Preheat the oven to 350°F. Spray a 13×9-inch baking pan with baking spray.
• In a large bowl, use an electric mixer to beat 3/4 cup (1 1/2 sticks) softened butter, 1 3/4 cups sugar, 3/4 teaspoon salt, 2 1/2 teaspoons baking powder, and 2 teaspoons vanilla extract until light and fluffy, about 5 minutes.
• Add the 4 large eggs and 2 egg yolks one at a time, beating well after each addition and scraping down the bowl as needed.
• Add 1 1/2 cups buttermilk and mix on low speed just until incorporated.
• Add 2 3/4 cups all-purpose flour and mix on low speed just until combined; scrape the sides and bottom of the bowl to ensure an even batter. Do not overmix.
• Pour the batter into the prepared 13×9-inch pan and smooth the top. Bake for about 35 minutes, or until the cake springs back when pressed lightly in the center (or a toothpick inserted into the center comes out with a few moist crumbs).
• Remove the cake from the oven and set it on a wire rack. While the cake cools slightly (it should be warm but not piping hot), make the icing.
• For the caramel icing: melt 6 tablespoons (3/4 stick) butter in a small saucepan over low heat. Turn the heat off and whisk in 1 cup packed light brown sugar and 1/4 cup milk until the sugar is dissolved and the mixture is smooth.
• Stir in 1 3/4 cups powdered sugar until the icing is smooth. If the icing is very runny, let it cool a couple of minutes until it thickens slightly, but do not let it set.
• Slowly pour the icing over the warm cake in the pan and spread gently if needed. Let the cake cool completely so the icing sets before slicing and serving.