Step 1

Using a sharp paring knife, peel three or four strips of lemon peel from the lemon. Skin should be about 1/2 inch wide and not have too much of the bitter pith or white part on it. Then juice the lemon, and set both zest and juice aside.

Step 2

Place blueberries and  water in a medium pot. Don’t worry about stems or leaves; they will be strained out later. Using a potato masher, crush the berries.

Step 3

Over medium-high heat, bring the berries and water to a boil, then lower the temperature to medium-low. Simmer berries for 15 minutes, stirring occasionally. They will darken considerably.

Step 4

Remove pot from heat and ladle berries into a fine sieve set over a heat-proof bowl or measuring cup. Using the back of a smaller ladle, press on the berry solids to extract as much juice as possible. Discard solids. (Update: or save them if you like. This part is apparently alarming to quite a few commenters! But my solids are full of stems, not worthy of a smoothie.)

Step 5

Return the blueberry juices to the pot, then add the lemon peel (not juice yet) and the sugar. Bring to a boil and simmer for about 10 minutes until the mixture thickens slightly. (Optional: Add a stick of cinnamon here, if you like).

Step 6

Add 2 tablespoons lemon juice and stir to combine. Boil another minute or two. Remove from heat and allow to cool. Remove lemon zest.

Step 7

Using a funnel, pour syrup into clean jars. Top with lid and store in the refrigerator for up to three months, or the freezer for up to nine.