01 - Preheat oven to 350°F. Grease and flour three 8-inch round cake pans or line with parchment paper.
02 - In a skillet over medium heat, melt 2 tablespoons butter. Add chopped pecans and toast, stirring frequently, until fragrant and golden, about 4-5 minutes. Transfer to a plate to cool.
03 - In a medium bowl, whisk together flour, baking powder, baking soda, and salt.
04 - In a large bowl, cream together 1 cup butter and sugar until light and fluffy, about 3 minutes. Beat in eggs one at a time, mixing well after each addition. Stir in vanilla extract.
05 - Add the dry ingredients to the 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 the tops. Bake for 25-30 minutes, or until a toothpick inserted into the center comes out clean. Let cakes 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 finely chopped pecans.
09 - Place one layer on a serving plate. Spread frosting over the top. Repeat with remaining layers. Frost the sides and top. Garnish with extra pecan halves if desired.