Answer: It sounds like a blossom bud to me! These can sometimes be infected with fungi, but yours sounds normal. Unfortunately, once an onion flowers, you should use it as soon as possilbe. If left to grow, the bulb gets tough, thin and off-flavor. I think your onions weathered a cold snap that made them think it was time to set seed. When onions of any kind feel cold (40-50F) for 10-14 days, and the stalks are 1/4" diameter or larger, they'll be stimulated to flower.
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