Step 1

Combine raspberries and sugar in a saucepan.

Step 2

Cook on medium-high heat until all the sugar has dissolved, about 20 minutes. Mash any remaining berry pieces.

Step 3

Pour the mixture through a fine mesh strainer. Strain twice if you want to ensure no pulp gets through. Add the lemon juice from two of the lemons.

Step 4

Boil the water, and then add it to the raspberry syrup in a large pitcher. Let the mixture cool, and then chill it all the way in the fridge.

Step 5

When you are ready to serve, slice the remaining lemon. Pour cordial into glasses and top with a lemon slice.