If you want diced onions, the cook generally wants onion chunks below a certain cubic mass, so they cook and dissolve easily and uniformly. It does not matter if some pieces are 50% of that size, some are 20% and some are 80%.
With that, 1-2 horizontal slices and a bunch of straight downward slices are the safest and easiest way to achieve that.
That technique also expands to onion rings, sauteed onions and such.
If you want diced onions, the cook generally wants onion chunks below a certain cubic mass, so they cook and dissolve easily and uniformly. It does not matter if some pieces are 50% of that size, some are 20% and some are 80%.
With that, 1-2 horizontal slices and a bunch of straight downward slices are the safest and easiest way to achieve that.
That technique also expands to onion rings, sauteed onions and such.