Preheat oven to 350°F (175°C). Grease and flour two 9-inch round cake pans.

Cream together butter and sugar until light and fluffy, about 5 minutes.

Add eggs one at a time, mixing well and then add vanilla extract.

In a separate bowl, whisk together flour, baking powder, baking soda, and salt.

Gradually mix dry ingredients into the wet mixture alternating with buttermilk.

Fold in toasted pecans until evenly distributed.

Divide batter into prepared pans and bake for 25-30 minutes, until a toothpick comes out clean.

Allow cakes to cool in pans for 10 minutes, then transfer to wire racks to cool completely.

For frosting, combine butter, brown sugar, and milk in a saucepan, boil, then mix in powdered sugar and vanilla until smooth.

Frost the cooled cakes, adding pecans on top if desired.