Add the lemon juice to a container that can be sealed (I used a quart-sized juice jar). Pour in the sugar and stir until the sugar is completely dissolved.

In a blender, puree the raspberries. To remove the seeds, pour and push the raspberry puree through a sieve into a bowl. Discard the seeds and pour the seedless puree into the container with the lemon juice. Stir to combine.

Slowly pour the club soda over the mixture and then gently stir (be careful; the soda can be really fizzy!).

Serve over ice and store leftovers in the refrigerator. This recipe makes 1 quart.