When you ask with WHO or WHAT, look at the answer. If the wh-word is the doer (subject), use no 'did' and the normal verb. If it is the receiver (object), use 'did' + base verb, like a normal question.
Practice tip: Ask: is the answer the DOER or the RECEIVER? Doer = no 'did' (Who won?). Receiver = use 'did' (Who did you beat?).