NASCAR 21: Ignition

Win 11x Races in EITHER Career OR Race Now mode. It does not combine the number of wins in both modes for this.

While you wil get this working through Career mode, should you wish to do it in Race Now mode then the below is the simplest way to win a race:

Options (main menu) > Difficulty and Assists
AI difficulty: Novice

Race Now:
Track: Daytona Road

Settings:
Race Type: Race Session only
Race Length: 2%
Field Size: 2+
NASCAR rules: Off

Start Weekend then Use Datapad > Options > Difficulty and assists.
Driving Line: On
Braking Assist: Off
Steering Assist: Low or off

So the joy of this track is that the two chicanes become optional, thanks to NASCAR rules being off. Blast through the traffic cone 'barriers' and you'll suffer no penalties and win with ease. With these settings on an average run I was getting a time of ~1:40.