"I had a cake." means you ate the whole cake by yourself. -------- "I had a piece of cake." means you ate only a portion of the cake. -------- You will more often want to say "I had some cake." because it does not specify how much cake you ate just simply that you ate cake. -------- Saying "I had some cakes." means you ate more than one cake by yourself. -------- "I had a cake." and "I had some cakes." should be avoided as they sound funny.

I had a cake = I had one entire cake I had a piece of cake = I had a slice of a cake you can say "I had some cake" if you do not wish to specify exactly how much cake you had.

Actually, you should say: "I had SOME cake." (= I had a piece (or two) of cake) A cake = a whole cake, and that might make you sick.

It was a party, there were many cakes, but you only had one cake, and you wanted to share it with me, so you cut a piece of cake for me. picture it.

Yum, I'd like a piece of that cake.