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 a skillet over medium heat. Add chopped pecans and toast, stirring frequently, until fragrant and golden, about 4-5 minutes. Transfer to a plate to cool completely.
03 - Whisk together flour, baking powder, baking soda, and salt in a medium bowl until well blended.
04 - Beat 1 cup butter and granulated sugar in a 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 butter mixture in three batches, alternating with buttermilk. Begin and end with flour mixture. Mix until just combined, being careful not to overmix.
06 - Gently fold in all but 1/2 cup of the toasted pecans. Reserve the remaining pecans for the frosting.
07 - Divide batter evenly among prepared pans. Smooth tops and bake for 25-30 minutes, or until a toothpick inserted into the 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 and spreadable. Adjust consistency with additional cream if needed. Fold in reserved chopped pecans.
09 - Place one cake layer on a serving plate. Spread frosting over the top. Repeat with remaining layers. Frost the sides and top of the cake. Garnish with additional pecan halves if desired.