lemon butter cake

Copy and tested from : 
https://phonghongbakes.blogspot.co.uk/2014/10/lemon-butter-cake.html

Mixture A :

250g butter at room temperature 

80g fine sugar

1 teaspoon vanilla extract

4 egg yolks

200g self raising flour (sifted)

Zest from 2 Lemons
2 tablespoons lemon juice

Mixture B :

4 egg whites

80g fine sugar

Method :

1. Cream butter and sugar until light and fluffy. Add vanilla essence.

2. Add egg yolks one at a time, beating well after each addition. 
3. Then add lemon zest.

4. Add flour in three additions. In the first addition, add 1 tablespoon of lemon juice. Fold in the flour until just incorporated. In the next addition, add in second tablespoon of lemon juice and mix. Then add in last addition of flour. Do not over mix.

5. In another bowl, whisk egg whites and gradually add sugar. Whisk until stiff peaks.

6. Fold in 1/3 of egg whites into the butter mixture. Mix well and fold in the remaining egg whites.

7. Bake in a greased and lined 8" round pan at 160C for 50 minutes or until skewer inserted into the centre of the cake comes out clean. (don't over bake)

Notes for my future reference :
a) After step 2 above, I used a spatula to mix in the lemon zest and to fold in the flour.
b) I baked this cake on the lower rack and tented the cake with aluminium foil during the last 10 minutes of baking.