Lemon Syrup (Cordial)

Gluten Free. Dairy Free. Vegan.
This recipe has been around since the 12th century. It is completely scalable. Also, it is an easy way to use up lemon juice when you are making candied lemon peel.
​Ingredients

• 500mils of Lemon Juice
• 500grams of Sugar

Method

• Prepare glass bottles by putting them on a tray and pouring boiling water over them and the lids. I pick them up using tongs. Put on a tray and dry in the oven on 105 degrees Celsius for 10 minutes. If the lids have a plastic coating, submerge them in a bowl of boiling water and then air dry them.
• Prepare bottles
• Freshly squeeze lemons.
• Measure out lemon juice and sugar into a saucepan.
• Simmer on medium stirring occasionally.
• Once it thickens into a syrup it let it cool slightly
• Pour hot mixture into bottles carefully using a metal funnel. Place the lids on firmly. Gently tip the bottles to the side and rotate so that the heat of the mixture kills any potential bacteria left on the lid. Store in cupboard. 

Background
Syrup of Lemon
“Take lemon, after peeling off the skin, press it [to a pulp] and take a ratl [1 ratl=468g/1lb] 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.”
Source: page 18 Anonymous Andalusian Cookbook Kitab al tabikh fi-l-Maghrib wa-l-Andalus fi `asr al-Muwahhidin, li-mu'allif majhul. The Book of Cooking in Maghreb and Andalus in the era of Almohads, by an unknown author.

[88] To make Syrupe of Lymonds. Take your Lymonds, and cut them in halfes, and betwixt your fingers juyce them, and the liquor that runnes from them wil be very cleare, then take to a pint of juyce, a pound and a quarter of hard suger, which is very white and boyle it to a Syrupe, and it will keepe excellent well.
A Closet for Ladies and Gentlewomen (1608) London: Printed [by F. Kingston] for Arthur Iohnson,1608