I've been drinking kvass since childhood (my parents used to make it), and now that I brew, I make it for them.
To be honest, I've never seen or heard of it made with malted barley. Rye or wheat bread (rye is better IMO) is pretty much the main ingredient. And traditional kvass most definitely does not have lemon peels. It is also quite sour.
I did a few batches with used steeping grains, and all they did was add a bit of color but I suppose using malted rye or wheat could be OK... But anyway, try what you feel is right. There aren't guidelines for making it, other than keeping OG at about 1025, because it's a summer drink, intended to quench thirst and get back to work rather than quench thirst and knock you out on the lawn
Basic recipe is this:
Dry and toast about a loaf of rye bread. The darker you toast, the darker kvass will be, but don't burn it. Heat up about 3-4 gal of water. You can boil it if you want, but it won't make any difference. Put your dry bread into a bucket, and pour the hot water in.
Now here, you can either add some sugar to this "wort" or you can mash some grains in that water, like you do with beer, before pouring it over the bread. That's pretty much it. Ferment with the bread in there. I usually use baker's yeast and ferment at room temperature, but tried Nottingham and found it gives drier result. If using beer yeast, ferment cooler to avoid unpleasant flavors... unless you're using belgian yeast... hmmm I'll have to try that. And don't keep it in there for long because after some time it'll get "stale bread" flavor.
Usually it is done in 4-5 days. Keep tasting it as it gets more sour with age. By day 5 it's sour enough for me. Then you can bottle it like beer and wait 2 weeks to carb (when I do that, I use plastic and use about 1 cup sucrose for 3-4 gallon) or you can keg it and enjoy in a day. It'll be pale straw color if you don't use color grains.
Maybe this isn't what you're after, but this sour bread thing is what kvass is. These days there is black kvass that tastes like tar with sugar and other cloying junk that you can buy in a store. So if you're after the sweet stuff, I can't help you.