Heat a large heavy non-stick skillet over medium high heat. Add oil to the hot pan and place broccoli cut side down, leaving undisturbed for about 3 minutes until golden brown.
Add garlic, lemon zest and a pinch of salt, toss and cook for 30 seconds. Lean pan to the side and carefully blot any excess oil with a clean paper towel, held with tongs. To the pan add butter, red pepper flakes and water. Cover and cook about 1 min for crisp, 2 min for crisp tender or 3 min for very tender. Serve immediately.
Cutting the florets in half lengthwise through the stem gives more flat surface area for better caramelization. Make sure to leave a good amount of the stem attached, and not just the top part of the floret.