focus could be a little bit better and the "spaghetti" in the background is more of a distraction than a help I think, nice perspective though - I feel like I might cry!
The arrangement and composition is fine in this image but the softer focus loses fine detail that the eye would like to see and that acts as a visual distraction. Looks like the background is in sharper focus than the onion. Shooting at a higher f/stop would increase DOF and eliminate that problem.
This isn't a culinary challenge, so I won't speak about your diced onions. The composition is alright, but I would have thought having the other half onion a bit further away might be better. I'm not exactly sure what's wrong with the picture, but something isn't work well and it throws me off quite a bit. Maybe it's because it looks like you've got a camera flash going on.
I must admit the frames should have been a lot thinner. It's too thick and it causes quite a lot of distraction to the whole image. So I threw you a 5.