OK, quite bizarre. Have a reply from 'Contra Costa Master Gardeners Help Desk' which explains that the red dots are Extrafloral nectaries, amazing.

I was going to say probably nectaries so glad we have a correct answer. is it not a hardy cherry? Just wonder why you haven't put it in the ground. Or is it still a baby.

Yes, I am interested to know why its being grown under glass too. Maybe its the variety. When I moved to Scotland, I never saw any fruiting Cherries, and assumed they weren’t hardy enough for our East Coast climate (I am in Angus). But one year I was out walking and came upon two heavily laden big Cherry trees at Barry Mill. I cheekily ‘stole’ a handful and they were the best cherries I have ever tasted! I don’t grow them though...because the birds always seem to steal them well before they are ripe. I think you need a big mature tree in order to get enough to ‘share’ with the feathered friends! Perhaps they are under glass for this reason?

I'm more familiar with peaches, plums and apricots, but I wouldn't be surprised if all of the stone fruit had two or more nectaries at the base of each leaf.