Preparation Steps

• Preheat the oven to 350°F (175°C). Grease and flour a 9x13-inch baking pan or line with parchment.
• In a medium bowl whisk together the all-purpose flour, baking powder, baking soda, and salt; set aside.
• In the bowl of a stand mixer, cream the softened unsalted butter with light brown sugar and granulated sugar on medium speed until light and fluffy, about 3 to 4 minutes.
• Add the eggs one at a time, beating well after each addition, then mix in the vanilla extract.
• With the mixer on low, alternately add the dry ingredients and buttermilk in three additions, beginning and ending with the dry ingredients. Mix until just combined; do not overmix.
• Fold in the butterscotch chips by hand until evenly distributed through the batter.
• Spread the batter evenly into the prepared pan and bake for 30 to 35 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs.
• While the cake bakes, make the caramel icing: combine 0.5 cup unsalted butter and 1.0 cup light brown sugar in a small saucepan over medium heat. Stir until the butter melts and the sugar dissolves.
• Carefully whisk in the warm heavy cream. Bring to a gentle simmer and cook for 2 to 3 minutes, stirring constantly, then remove from heat and stir in vanilla and 0.25 teaspoon salt. Allow the icing to cool slightly so it thickens.
• When the cake is done, let it cool in the pan for 10 minutes, then prick the top lightly with a skewer and pour the warm caramel icing over the cake so it absorbs into the crumb. Cool completely before slicing.