This is the best way to dice an onion quickly and evenly. As you are learning the technique, it may feel slower in the beginning, but once you practice a bit, you can knock out quite a few onions in the time it used to take to do one. It also offers you more control: adjust the thickness of the dice by spacing out your cuts to your liking.
Slice the onion in half from head to root. Take off the outer skin and lay the onion flat on your cutting board and slice off the tops off of the two halves. You want to keep the root on and intact because it will keep the whole situation together.
Make one or a few horizontal cuts through the onion (depending on how thick the onion is). Stop before you reach the end of the root.
Next, hold the sides of the onion, and make vertical cuts through the onion. Again, don’t cut into the root.
If you have a paring knife, you can use it to make the horizontal and vertical cuts. I’ve survived without one for 7 years, so I think you will be okay.
Now, take your chefs knife and slice the onion across the first 2 cuts so you have a nice dice. Slice all the way up until you hit the root. If there are a few stubborn big pieces, you can rock the knife through a few times.
Song: The Roots - Break you off