Was it the 'fertilizer'?

I pulled an onion out of the garden Thursday and before it got put into the supper pot, I had to take a photo. OK, I know your onions are likely bigger but this is the biggest I've ever grown. Should say "we" since J and I planted them and Joel's done lots of watering. We've three garden boxes and in the spring were rather frustrated with the neighbour's cat who thought one was its own litter box. By the end of June, fortunately, the cat couldn't find room in the box or the layers of cayenne pepper actually worked. However, we've noticed that the 'cat's box' has produced a lot plus big onions.