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 a time, mixing well after each addition. Stir in vanilla extract.
05 - Add dry ingredients to wet ingredients in three batches, alternating with buttermilk, beginning and ending with flour mixture. Mix until just combined.
06 - Fold in most of the toasted pecans, reserving 1/2 cup for frosting.
07 - Divide batter evenly among prepared pans. Smooth tops. Bake for 25-30 minutes or until toothpick inserted into center comes out clean. Cool in pans for 10 minutes, then turn out onto wire racks to cool completely.
08 - Beat 1 cup butter until creamy. Gradually add powdered sugar, beating until smooth. Add vanilla and heavy cream, beating until fluffy. Adjust consistency with more cream if needed. Fold in reserved chopped pecans.
09 - Place one layer on serving plate. Spread frosting over top. Repeat with remaining layers. Frost sides and top. Garnish with extra pecan halves if desired.