For the Rhubarb Rose Lemon Fizz:

(1) Shake the lemon juice, rhubarb syrup, rose water and egg white in a cocktail shaker filled with ice. Strain into a small, chilled glass (a coupe or a bistro glass works well) and top with tonic water (about 2 ounces).

For the Rhubarb Syrup:

(1) Combine the chopped rhubarb in a saucepan with water, sugar, and split vanilla bean. Bring to a boil over medium-high heat, stirring occasionally, then lower heat and cover. Let simmer gently for 5 minutes, then remove from heat.

(2) Stir in the orange blossom water, replace lid, and let cool to room temp. Refrigerate overnight, then strain with a nut milk bag or a cheesecloth-covered sieve. Reserve the strained, broken down rhubarb for use as a compote, and store both syrup and compote in the fridge.

[TIP: you can make the syrup without the orange blossom water -- it will still be awesome.]