Making nice cakes involve precise measurements. One cannot skip or add extra ingredients. For e.g., my cake recipe needs only 4 eggs. On that day, my naughty toddler had cracked 5 eggs which I just bought from the supermarket. Therefore, I used 5 eggs. The cake turned out a bit hard and crispy on the outside.
The butter and sugar must be beaten fast and hard to avoid the butter melting too much. The butter and sugar has to end up fluffy and white. To get the best result, use a electric cake mixer. Nowadays, they are sold for less than RM100.
Add in egg one by one, alternating with flour. I.e. One egg, fold (as in gentle motion with a wooden spoon), add flour, fold, one egg, fold, flour etc.
I was making marble butter cake. So, just take out one quarter of the batter (after completed mixing) and add some cocoa powder plus some cooking chocolate.
Just plop the chocolate and white portion alternately. Then swirl with a chopstick.
Note that some cracks appeared on the top of the cake? It is because the cake tin is too small and there is not enough place for the cake to rise.