01 - Preheat oven to 350°F. Grease and flour three 8-inch round cake pans or line with parchment paper.
02 - Melt 2 tablespoons butter in skillet over medium heat. Add chopped pecans and toast, stirring frequently, until fragrant and golden, about 4-5 minutes. Transfer to plate to cool.
03 - Whisk together flour, baking powder, baking soda, and salt in medium bowl.
04 - Beat 1 cup butter and sugar in large bowl until light and fluffy, about 3 minutes. Add eggs one at time, mixing well after each. Stir in vanilla.
05 - Add dry ingredients to wet mixture in three batches, alternating with buttermilk, beginning and ending with flour. Mix until just combined.
06 - Fold in most toasted pecans, reserving 1/2 cup for frosting.
07 - Divide batter evenly among prepared pans. Smooth tops. Bake 25-30 minutes or until toothpick inserted in center comes out clean.
08 - Let cakes cool in pans 10 minutes, then turn out onto wire racks to cool completely.
09 - Beat 1 cup butter until creamy. Gradually add powdered sugar, beating until smooth. Add vanilla and heavy cream, beating until fluffy. Adjust with more cream if needed. Fold in reserved pecans.
10 - Place one layer on serving plate. Spread frosting over top. Repeat with remaining layers. Frost sides and top. Garnish with pecan halves if desired.