Starting cake bking

You are probably better off posting this on a cake website. And only a cup of flour? Are you trying to do one of those microwave cakes? That seems like a lot of baking powder.

Try adding milk. It looks a little dry. Something more like this:

• 1 cup white sugar
• 1/2 cup butter
• 2 eggs
• 2 teaspoons vanilla extract

• 1 1/2 cups all-purpose flour
• 1 3/4 teaspoons baking powder
• 1/2 cup milk

1. Preheat oven to 350 degrees F (175 degrees C). Grease and flour a 9x9 inch pan or line a muffin pan with paper liners.
2. In a medium bowl, cream together the sugar and butter. Beat in the eggs, one at a time, then stir in the vanilla. Combine flour and baking powder, add to the creamed mixture and mix well. Finally stir in the milk until batter is smooth. Pour or spoon batter into the prepared pan.
3. Bake for 30 to 40 minutes in the preheated oven. For cupcakes, bake 20 to 25 minutes. Cake is done when it springs back to the touch.

The recipe looks more like a cookie recipe.  High in butter, low in liquids.  More like a quick bread or biscuit (USA).

Do you mean "cake" or where you trying to make "bread?"  Translators can sometimes change words around.  Never mind, practically the only difference between them are the words.

If you are trying to make a bread recipe, like a brioche, increase the flour to 500g and change the baking powder to  1 Tbs instant yeast. Put the eggs into a large cup and add enough water or milk  to make 300g.   Give the dough a warm place to rise for many hours.  Deflate when almost double and shape into a loaf to rise again to almost double from original volume.   Bake at 200°C for 45 minutes.

If you are after a cake, then cream the butter and sugar together until light and fluffy.  Separate the eggs and beat the whites into a stiff foam (stiff enough to turn the bowl upside down) and set aside.  Drop the yolks one by one into the "creamed§ sugar and eggs adding the pinch of salt.  Sift the baking powder into the flour and by hand, alternate part of the flour mixture with a some of the egg white folding in until all the flour and egg whites are incorporated.  If the mixture seems too thick and the egg white foam crushing, add a splash of milk before adding more flour.

Irregular bubbles are caused by lumps in the baking powder, always sift baking powder before using.  For most cakes, separate the eggs and beat the whites folding them in after all the mixing is done.  Eggs are fatty and blend better with the butter and sugar.   Use a lower baking temperature.  Try 175°C.  

Edit:  I just realised Maverick beat me to a reply.    My server is just too slow!   Mine is less sweet and perhaps heavier.  Other ingredients can be grated lemon or orange peel, a shot of liqueur.