Carrot-Apple Spice Cake with Browned-Butter Glaze

We set ourselves the task of creating an amazing dessert that uses the cake mix in the package as the starting point-and we succeeded. Fresh carrots and an apple plus a dash of bourbon enhance the flavor of the layers, and the browned butter frosting is, in general, an incredibly delicious icing on the cake.
Preheat the oven to 350 degrees.To make the pie, combine the first 5 ingredients in a large bowl; beat with a mixer on low speed for 1 minute or until smooth. Add the cake mix to the buttermilk mixture; beat on medium speed for 1 minute or until smooth. Add the carrot and apple until smooth. Spread the batter evenly over 3 (8-inch) round cake tins smeared with baking spray. Bake at 350 ° C for 20 minutes or until a wooden stick inserted in the middle comes out clean. Cool the cakes in the molds on a wire rack for 10 minutes. Remove the cakes from the pan; cool completely on a wire rack.To make the frosting, melt the butter in a small saucepan over medium-low heat; cook for 6 minutes or until lightly browned, stirring frequently. Allow to cool slightly. Combine the browned butter, 1 1/2 cups powdered sugar, cream cheese, milk, vanilla, and salt in a medium bowl; beat with a mixer on low speed for 2 minutes or until smooth.To assemble the cake, place 1 cake on a plate; spread 1/4 cup icing over the cake. Top with a second layer and spread 1/4 cup of icing. Top with a third layer. Combine the remaining 1/2 cup powdered sugar with the remaining icing. Spread the remaining icing on top of the cake. Sprinkle with chopped pecans.