Pyramid of Power 
1min at 20spm (rest 1min)
1min at 22spm (rest 1min)
1min at 24spm (rest 1min)
1min at 22spm (rest 1min)
1min at 20spm (rest 2min)
Repeat three more times.
DF 120

The notes suggest this should be done at max power for each interval - 10/10 RPE. Pacing guidelines in ErgZone were on the moderate side - if you try this again, nudge the pace up by +5 seconds each interval.