Sri Lanka A is firmly in control with a lead of 370 runs at stumps on day two in their second unofficial Test against West Indies "A" at Florence Hall.
He received support from off-spinner Shehan Jayasuriya with two for eight.
In their second turn at the crease, Sri Lanka A were slumping at 38 for four before Roshen Silva struck a fine unbeaten 85 to bolster the innings, with help from Dasun Shanaka with 60 and Jayasuriya, 32.
West Indies Women completed 3-0 series whitewash over Sri Lanka in the final One-Day International (ODI) at the Brian Lara Cricket Academy in South Trinidad on Sunday, as part of the ICC Women's Championships for qualification to World Cup 2021.
Cornwall was the leading bowler, picking up three for 70 with his off-breaks.
Buoyed by the huge lead, Sri Lanka nearly lost their advantage, slumping to 86 for five before a sixth-wicket stand of 128 between Silva, unbeaten on 85 and Shanaka, 60, turned the match firmly back in favour of the visitors going into Saturday's third day.
It soon became 69 for seven when Asith Fernando trapped Sunil Ambris lbw for 29.
However, Windies A struck back quickly as Cornwall, introduced early, grabbed two top order wickets and seamers Cottrell and Oshane Thomas both made key strikes to leave Sri Lanka A on the back foot on 57 for four at tea.
Asked to chase an improbable target of 425 at the Trelawny Multi-Purpose Stadium, the hosts tumbled to 144 all out in their second innings, following up their meek first innings of 137 on Friday.
Scores in the match entering Saturday's third day are: Sri Lanka "A" 294 and 213-6; West Indies "A" 137.