The easiest race to get this is the first career event called 'New Union Race' at California -Pacific Way.
In this event there are only 5 opponents and the race is fairly short and the track isn't too challenging you don't need to brake at all, only let off the accelerator.
Make sure that you have your Difficutly in 'Options & Extras' is set to Very Hard, note you can leave damage off. Make sure you do not use any flashbacks at any time.
If you have already passed this event you can retry it from the Timeline.
Here's a video of me doing it.