The achievement can only be earned at the end of the Flowery Field level.
After defeating a few waves of bees and beekeepers, you will be instructed to get into a catapult that will launch you into the next area. The catapult has a meter that rises and falls and your goal is to press
when the meter is completely full.
You may have to replay the level a couple of times in order to get the timing down. I found that I had to press the button just before the meter got full for it to launch me at maximum power.