Translation:I would have made a cake if I had had time.
Don't trust in the pronunciation of "bolo" because it's wrong. I reported this for duolingo. Although, "bolo" seems like "bowl" with the "o" in the end, I could write "bowlow".
That's it. I hope it helps someone.
Listened to "bolo" + ten times and still did not make out the word. Still bad audio Dec 15
"I would have made a cake if I had time" or "I would have made a cake if I had the time." are far better translations in my opinion
Leaving out the first had in the "if" clause changes the focus from a past condition to a present condition/situation.
The past condition reflects impossibility (often linked to regret) while the present condition indicates a slight possibility.
Those would translate as "Eu teria feito um bolo se eu tivesse tempo", without "tido"! The sentences you suggest would carry a general meaning, the person would mean he would have baked if he had time in general, whereas "se eu tivesse tido tempo" sounds more like the guy didn't have time in a specific situation or period of time.
As emeyr says, you really need both, but I'd abbreviate to 'if I'd had time' to make it sound better.
"Would" is only needed in the "result" clause, not the "condition" clause.
I would have made a cake if I had had (I'd had) time.
• Se eu soubesse que você estava chegando, teria feito um bolo.
• If I knew you were coming, I'd have baked a cake.
Annoyingly Duo added 'only' to the word list allowing 'I would have made a cake if I had ONLY had time. Only then to reject for adding the extra 'only' which wouldhave made it read better in English avoiding 'had had'