As Everton buckled, substitute Leon Bailey made it 3-0 with a powerful drive after coming on as a substitute although his cameo performance was curtailed by an injury
The closest an injury-hit Everton came to scoring was moments before Cash's opener when in-form Demarai Gray curled a shot just wide.
Everton have 10 points from five games in fifth spot with Villa moving up into the top half of the table with seven points from their five games.
Rafa Benitez's side were content to sit deep and play on the break, and they had been enjoying a degree of control until they were blown away by a stunning Villa burst.
Cash, who had never scored for the Midlands club before, was played in down the right before cutting in on his left foot and sending a rising drive past Asmir Begovic.
Everton were rattled and fell further behind when Bailey's corner glanced off Digne and into the net.
Bailey, whose pace was electrifying, then latched on to a bouncing ball down the left and lashed a ferocious shot into the back of the net with Begovic beaten for pace.
"I thought we were the better team in the first half but didn't create as many clear-cut chances as we'd like. I felt five minutes before our goal, they were on top," Villa manager Dean Smith said.
He reserved special praise for Bailey: "Leon put the corner in for the goal and scored the third. The first goal was great build-up and Matt [Cash] has put it in the top bin.
"I thought Leon would lift us a bit. He's really special. He's a really good player. That's why we got him here."