Two goals in three minutes, from Rowan Vine and Dave Mackay, made the difference midway through the second half as Saints leapfrogged Aberdeen into fifth place in the Clydesdale Bank Premier League.
Gregory Tade had opened the scoring with his second one-on-one in two minutes but Niall McGinn levelled for the Dons just before the break.
Lomas said: "It was a great win and well deserved. The lads responded very well and I thought it was a comfortable win.
"Gregory did so well with the opener because he had just missed a chance. He could have been forgiven for snatching at the second chance but he was very composed.
"We looked pretty comfortable but then a little slip from Callum (Davidson) and (Josh) Magennis got past him and they got a goal just before half-time.
"That could have caused a problem psychologically but the boys stuck to their task.
"Michael Doughty came on when they were having too much of the ball and freshened it up.
"To get two goals in two minutes was brilliant and we could have got more.
"It has been our Achilles heel all season but in key periods we were ruthless in front of goal."
- Sports & Recreation