**On the custom control system I use
for Gear Up and
for throttle so this may be different for you(you do get on screen prompts though)
First off, change the settings so Starting is set to "Manual".
At the beginning of the race, when prompted, hold gear up and then hold the accelerator at about 80% pressure. The display in the bottom corner should change from "Reach optimal revs" to "Maintain optimal revs", and the text will turn white.
When all 5 red lights go out, let go of Gear Up and press the accelerator fully.
You do not need to get off to a good start, just make sure you don't jump start.
Do all that for 10 races(I believe it's for any mode but I haven't touched anything but Career and Time Trial)
If you do get a penalty, you can restart the race and try again.
Credit to gesterx - "Good solution - You can actually get this by restarting the same race 10 times. You just have to wait about 3-5 seconds after the race start. Got it earlier in 3 minutes."