Combine chopped rhubarb, granulated sugar, and 1 cup water in a medium saucepan. Bring to a simmer over medium heat, stirring occasionally, and cook until rhubarb breaks down and mixture is thick and jammy, about 8–10 minutes.

Strain syrup

Remove from heat and let cool slightly (5 minutes). Pour the mixture through a fine-mesh sieve into a bowl, pressing gently on solids to extract as much liquid as possible. Discard solids or reserve for yogurt/ice cream.

Finish shrub

Stir the hot rhubarb syrup into the apple cider vinegar, then add rosewater and lemon juice. Taste and adjust: add up to another 1/4 tsp rosewater if you want more floral character, or a splash more vinegar if you prefer brighter acidity. Cool to room temperature, then refrigerate. Shrub will keep refrigerated for 2–3 weeks.

Cocktail (per serving)

Fill a cocktail shaker with ice (about 1 cup).

Add blanco tequila (2 oz), rhubarb-rose shrub (1 oz), fresh lime juice (3/4 oz), and honey syrup (1:1 honey to water, 1/2 oz) to the shaker.

Shake vigorously for 10–12 seconds until well chilled (shaker becomes frosty).

Fill a highball or Collins glass with fresh ice. Double-strain the shaken mixture into the glass to remove any ice shards and ensure clarity.

Top with club soda (about 2 oz) and gently stir once or twice to integrate.

Garnish with an edible rose petal or a long ribbon of rhubarb and serve with a straw or stirring stick.