I'm not good at making cakes

So I bought one for your birthday instead!

It's Kenzo's birthday soon and so we went to T&T to buy a nice fruit cake. That's not the one, but it looks similar.

How do you say "I'm not good at making cakes"?

You need to use のが which transforms a verb into a gerund. In this cake - I mean, case - we use the verb for make in short form.

to make: つくる　（作る）

to make in short form: 作る　(it stays the same because positive short form for verbs is the same as dictionary form)

making: 作るのが

making cakes: ケーキを作るのが

I'm not good at making cakes.

ケーキを作るのが上手じゃない。

So, I buy them at T&T.

だから、T&T でかう。