Add strawberries to the bowl of a food processor. Purée until smooth. (If necessary, you can add a tablespoon or two of water to get the blades moving.)

Pass strawberry purée through a fine mesh strainer to remove the seeds.

In a 1-liter jug or pitcher, whisk together the water and lemon juice.

Whisk in the rhubarb simple syrup, followed by the puréed strawberries.

Chill until ready to serve.

Pour over ice. Garnish with lemon slices and fresh strawberries.

Store leftover lemonade in the refrigerator for up to 1 week.