If you sowed it last spring then it should have been harvested last year. This year it would have flowered and the elongation of the stem in your picture indicates it was about to. Onions can be tricky and in less than optimal conditions often don't 'bulb up' giving you a thin stem as in your picture. Unless, of course you planted what we call 'Spring onions' and I believe you call scallions, which are not meant to bulb up.

My bad. I planted a few n just let it be didnt take much care with them. And it did have a flower starting.
Terry