Cook first 3 ingredients in a small saucepan over low heat, stirring constantly, until butter melts and mixture is smooth; remove from heat.
Beat buttermilk and next 3 ingredients at medium speed with an electric mixer until smooth; add cocoa mixture, beating until blended.
Combine sugar, flour, and salt; gradually add to buttermilk mixture, beating just until blended. (Batter will be thin.) Pour batter into a greased and floured 15- x 10-inch jelly-roll pan.
Bake at 350° for 20 to 25 minutes or until a wooden pick inserted in center comes out clean. Cool cake completely in pan on a wire rack.
Pour warm Quick Caramel Frosting over cake, spreading evenly to edges of pan. Sprinkle evenly with pecans.