Spray three 8-inch pans generously with baking spray and flour. Cut circles of parchment paper or wax paper to fit pans and place one in the bottom of each pan.
Combine cake flour, baking powder, and salt together; set aside.
(If you are using the extra fine cake flour you won't need to sift the flour, if not put the flour, baking powder and salt through a sifter.)
Beat butter and sugar in the bowl of an electric mixer until light and fluffy.
Add vanilla and then eggs one at a time, beating after each addition.
Add flour mixture and milk alternately in 3 batches, beating until smooth after each addition.
Divide batter between prepared pans.
Bake until golden, 25-30 minutes.
Let cool on a rack for 10 minutes; invert cakes onto a cooling rack; let cool completely.
Brush off crumbs from sides and top of cake.
Place one cake layer on a plate or cake stand.
Add icing and spread to cover. Repeat with remaining layers.
Frost entire cake with a generous layer of icing.
Place 1/2 cup butter, brown sugar and evaporated milk into a microwave safe bowl. Microwave for 1 minute, stir. Return to microwave and cook on high for 2-3 more minutes or until the mixture is smooth and no longer gritty. Can also be done in a saucepan on the stovetop. Heat until ingredients are combined and no longer gritty.
Cool mixture for 15 minutes.
Place in mixer and add in powdered sugar and mix on low until incorporated.
Turn to medium high and mix for another minute.
Add in 1/2 cup of softened butter and vanilla and mix on medium high for 3-4 minutes or until light and fluffy.
Frosting should be a nice spreadable consistency. Add more milk if too stiff or more sugar if too thin.