I got this easily by the below method.
Custom Championship
Add Event - Hell Norway (Rally Cross)
Format - Single Race
Vehicle Class - Anything (I chose RX Supercars 2019)
Weather - Daytime / Heavy Rain / Wet Surface (Heavy Rain is the key here)
Laps - 2
Confirm, then press
to change championship settings, set AI performance to Very Easy if required.... Apply it and Start Championship, chose a car then win the race, be sure to make 1 of the 2 laps a joker lap.
Cheev pops during the results screens.