Quick and Simple Plum Cake
I usually soften butter in the microwave for 12 to 15 seconds (exact time will depend on your microwave), if I forget to take the butter out of the refrigerator in advance.
If you are making the cake by hand, cream softened butter and sugar together, add eggs one at a time, and then the lemon zest. Add the flour (sifted together with baking powder and salt) alternately with the sour cream, adding a little at a time. Mix until light and smooth.