Using a sharp knife, and with your fingers well away from the blade, cut both ends off the onion.
Make a slit with the back of the knife from one end to the other. Peel off the skin and discard along with the ends.
Cut the onion in half.
Holding the onion in place with the hand that is not holding the knife, cut into 1/2 in. thick cross sections.
Turn onion and repeat the previous step.
Repeat above steps with the other half of the onion.