First cut off the ends of your onion. Then peel of the dried outer layer. It should look like this.
Cut your onion in half. Like so.
Lay the half onion on its side and make slices in it like this. Don't cut the slices all the way threw the onion. (length wise) Leave a space at the back like above.
This shows how to cut the slices In the onion and then the final step.
Here is a better view. After you cut the slices in the onion you then want to cut with a slightly downwards tilted motion like so working your way to the back end.
And now you have evenly finely chopped onions. :)
Thanks for checking out my guide!