Hi,
The Present Perfect is a very common topic of disussion on the Forum. If you search for it, you'll find many useful threads you can review. Very brieflY
I made the cake Simple Past just states a fact about the past. Perhaps you made the cake yesterday, perhaps last year. 'For my wedding in 1990, I made the cake.'
I have made the cake Present Perfect means you have right now the result of 'the making', which is usually the cake itself. 'I have made the cake. Would you like a piece? Let's eat!'
Best wishes, Clive