There are two ways of doing this.

You can draft another car and bumpdraft them. When on straights, press [Boost] to pull away from the pack. You must keep steady when using the boost; if you do not, the car in front of you will spin. To win you must boost around the car in front of you out of turn 4. You will then win the race easily.

Upgrade you car(s) to their maximum performance. Every time you go down the backstretch, hit the boost until it is gone. Do this in every lap and you will pull away from the pack and they can never get you.