Brown butter over medium low heat until golden, then cool completely
Preheat oven to 350°F and grease and line three 8 inch cake pans
Whisk flour, sugars, baking powder, baking soda, and salt until combined
Mix cooled browned butter into dry ingredients until incorporated
Whisk buttermilk, eggs, and vanilla, then add to batter and fold in pecans
Divide batter into pans and bake about 30 minutes until done, then cool completely
Beat butter, cream cheese, brown sugar, vanilla, and salt, then add powdered sugar and cream until fluffy
Level layers, stack with frosting, frost outside, and finish with pecans