1. Preheat the oven to 350°F. Grease and line three 8-inch cake pans with parchment paper.

2. Spread the pecans on a baking sheet and toast them for 6 to 8 minutes, until fragrant. Cool completely, then chop.

3. In a medium bowl, whisk together the flour, baking powder, and salt.

4. In a large mixing bowl, beat the butter, granulated sugar, and brown sugar until light and fluffy.

5. Add the eggs one at a time, beating well after each addition. Mix in the vanilla extract.

6. Add the dry ingredients in three additions, alternating with the buttermilk, beginning and ending with the dry ingredients. Mix just until combined.

7. Fold in the toasted chopped pecans.

8. Divide the batter evenly between the prepared pans and bake for 24 to 28 minutes, or until a toothpick inserted in the center comes out clean.

9. Cool the cakes in the pans for 10 minutes, then turn them out onto wire racks to cool completely.

10. For the frosting, beat the butter and cream cheese until smooth and creamy.

11. Add the powdered sugar, brown sugar, and vanilla extract. Beat until fluffy, adding heavy cream as needed for a smooth spreadable texture.

12. Place one cake layer on a serving plate, spread frosting on top, then repeat with the remaining layers.

13. Frost the top and sides of the cake and press chopped toasted pecans onto the sides or scatter them over the top.

14. Chill the cake for 20 minutes before slicing if you want cleaner layers, then serve.