You are the killer of Uncle Smith.
In fact, you wanted to kill Barbara, but it happened the way it did. The crime was committed at night while the whole house was asleep. You knew that Henry was away, so you entered the bedroom and fired a gun with a suppressor. Not thinking of anything better to do, you hid the gun in the dough and baked a cake in the morning.
If you're lucky, you'll be able to discreetly throw it away when it's done.
A week ago, you found an anonymous note in Henry's office (sometimes you were a maid and cleaned it): ‘Barbara is cheating on you!’. You passed the note to Salma, who asked you to keep quiet. It was not difficult for you to find out that Barbara was sleeping with Anthony. This fact angered you: ‘The ungrateful brute!’ - that's when you had the urge to kill her.