Butter Cake

I am satisfied with the taste and texture, but how to achieve the smooth surface like those selling at the bakery? Any ideas or tips? Original recipe is available at yochana's blog, I have reduced the amount of sugar as some people commented it was too sweet. Other than that, all good and will use this recipe again.

Recipe adapted from Yochana's Cake Delight

Ingredients (9”):
250 g Butter
85 g Sugar
1 tsp Vanilla Essence
A pinch of salt
4 Egg Yolks
1 tbsp Evaporated Milk
200 g Cake Flour
5 g Baking Powder

4 Egg Whites
85 g Sugar

Methods:

1. Preheat oven at 175ºC, grease and line a baking pan.
2. In a large mixing bowl, beat together butter, sugar, salt and vanilla essence until light and creamy.
3. Add in egg yolks, one at a time and beat until creamy. Add in evaporated milk and mix well.
4. Sifted together cake flour and baking powder, and fold into mixture.
5. In a separate mixing bowl, whisk egg whites until foamy then add in sugar gradually. Beat to a soft peak and fold ¼ into the creamed butter mixture, then fold in the rest.
6. Pour batter into baking pan and bake at 175ºC for about 45 minutes or until cooked (insert a skewer in the middle of cake and come out clean).