How to Slice a Bloomin' Onion: 1. Cut off 1/2 inch from the pointy stem end of the onion, then peel. 2. Place the onion cut-side down. Starting 1/2 inch from the root, make a downward cut all the way through to the board. 3. Repeat to make four evenly spaced cuts around the onion. 4. Continue slicing between each section until you have 16 evenly spaced cuts. 5. Turn the onion over and use your fingers to gently separate the outer pieces.