。
Mother made me a Christmas cake.
Literal
Mother [topic-は] Christmas cake [obj-を] made-for-me.
クリスマスケーキ is a cultural loan with a twist: in Japan, it refers specifically to the fluffy strawberry-and-whipped-cream sponge cake traditionally eaten on Christmas Eve, a post-war commercial invention that has nothing to do with the fruitcakes or yule logs of the Western Christmas. ~てくれた marks the favor as flowing to the speaker — the cake was made for them.