Question

pico la cebolla? no, no la

Answer 1

This barely makes sense to me. Is there supposed to be an accent mark over the O, in "pico"?

Answer 2

Pico with no accent is the present tense.
Picó with an accent on the o is the past tense.

Either way the question can make sense.

¿Picó la cebolla? No, no la picó.
Did he mince the onion? No he didn't

¿Pico la cebolla? No, no la piques.
Do I mince the onion? No, don't mince it.

Answer 3

I see what you mean. That was my mistake. For some reason, "picar" and "mince" did not click in my mind.

Answer 4

Right, the more common meaning of picar is to sting or to bite such as what a mosquito or bee does.