Piece of Cake

Question

How would you cut a rectangular cake into two equal pieces when a rectangular piece has already been cut out of it? The cut piece can be of any size and orientation. You are only allowed to make one straight cut.

Possible Solution

1.  The simplest solution that one might think of is to cut the cake horizontally along the height of the cake. That would divide the cake in exact two equal pieces.This solution won't work if there is some frosting on the top which also needs to be divided.
2. Other possible solution would be to make a cut such that it passes through center of both the rectangles. Since the cut halves both the rectangles, the resulting two pieces are guaranteed to have equal area.