For bottom layer, cream softened butter and brown sugar until light and fluffy.
Beat in egg yolks, blend well together.
Slowly add flour, baking powder, and salt.
Spread batter evenly in prepared baking pan.
For topping, whip egg whites and vanilla extract until foamy.
If you plan to use the same whisks that you have previously used to cream butter and sugar, please make sure that they are absolutely clean and free of any fat particles.
Slowly add brown sugar, and continue beating until soft peaks form.
Gently fold in chopped pecans and spread topping evenly over unbaked bottom layer.
Bake for about 25 minutes until meringue topping is lightly brown and firm to touch.
Cool completely in baking pan on wire rack before cutting.