How to Make It
Preheat oven to 350°F. Cook 1 cup of the pecans and 1 1/2 tablespoons of the butter in a small skillet over medium, stirring, until toasted, 6 to 8 minutes. Spread pecans on wax paper; cool about 10 minutes.
Meanwhile, beat remaining 1 cup butter with a heavy-duty stand mixer on medium speed until creamy; gradually add sugar, beating until light and fluffy. Add egg yolks, 1 at a time, beating just until blended after each addition. Stir in vanilla.
Stir together flour, baking soda, and salt; add to butter mixture alternately with buttermilk, beginning and ending with flour mixture. Beat at low speed until blended after each addition.
Beat egg whites on medium speed until stiff peaks form; fold one-third of egg whites into batter. Gently fold in remaining beaten egg whites just until blended.
Pour the mixture in a sheet pan, and bake at 350˚ for 50-55 minutes. Add the coconut pecan frosting.