Onion Anatomy and a quick cutting lesson

Anatomy of an Onion

Onions-peeled and unpeeled

The top of the onion (where the finger is pointing) is the part that sticks out above the ground. The root of the onion is what is below the soil.

Using a sharp knife, make vertical slices into the onion, down to the root.

Now, make horizontal slices, across the vertical ones you just made.

Lay the onion on it's side and slice through your cuts. 

You should have nicely sized onion squares that are perfect for sautéing or salads. 

FYI~ If you only need half an onion and plan on saving the rest of it for another meal...you should always cut your onion from the top to the bottom. All of the flavor is retained in the root end. So, if you start at the bottom, the onion will lose it's flavor faster.