In historical recreation circles you often hear about people using an updated version of this receipt they use to make lemonade. Despite the assurances that this was medieval lemonade, I can tell you that it is unlikely that this was served on a regular basis. Like most of the syrup beverages in the Al-Andulus this is meant to be a medicinal recipe.
This particular syrup would have been administered as a syrup to someone showing signs of what was called a bilious fever, which is an illness that involves a fever accompanied by a lot of nausea and vomiting, in addition to someone who has loose bowels.
It doesn’t make good lemonade. Cooking the juice detracts from the flavor and it also ruins the Vitamin C-complex just a little. I will give you the directions for a good sour mix at the end of this post.
Take lemon, after peeling off the skin, press it [to a pulp] and take a ratl [1 lb] of juice, and add as much of sugar. Cook it until it takes the form of a syrup. Its advantages are for the heat of bile; it cuts the thirst and binds the bowels. [i]The Book of Cooking in Maghreb and Andalus in the Era of Almohad
Some translators take this recipe to mean that one should press the oil from the skin for flavoring. I have a slightly different take on it though. I know that the pith of the lemon contains a good deal of a nutrient known as rutin which is thought to be an antioxidant is beneficial to an overloaded liver. I also know that including the pith in remedies for the flux was practiced in later years. My very educated guess is that it is most likely that the author meant for the pith to be ground and included in the recipe.
When I make this as a remedy, I thinly peel some lemons and I usually put the peels in a vinegar to infuse, because I am frugal like that. Alternatively, you could make limoncello.
Then I use my pastry blender to mash the rest of the lemons, pith and all, until it makes enough liquid. You could also just give them a good whir in a blender. For what it is worth a pound of liquid isn’t quite 16 fl. ounces, it is about 15.34 ounces. Then I add one pound of sugar.
Then simmer for about five-seven minutes. This is not going to set up like a thick modern syrup with added emulsifiers. Think of a simple syrup or those used for coffee flavorings. If you cook it longer, you destroy some of the flavor and you run the risk of something that goes to soft crack stage and won’t dissolve again. (If you ever do that by accident, all is not lost. Pour the syrup into little dollops on parchment and let it harden to lemon hard candy.)
To make a flavorful homemade sour mix that you can use as a lemonade concentrate, I zest a couple of lemons and a lime into two cups of water and then add two cups of sugar and make a quick simple syrup with that. Then I let it cool, strain out the zest and add an equal amount of fresh squeezed juice. I like sour so I go a little heavy with lime juice. This stores in bottles in your fridge for a couple of months.
[i] Anon. The Book of Cooking in Maghreb and Andalus in the Era of Almohads. Translated by Martinelli, Candida. 2012 translation. Al-Andulus, Spain: CreateSpace Independent Publishing Platform, ca. 1400.