Combine vodka, lemon juice and sumac syrup in a bar tin with ice and shake vigorously for 15 seconds. Strain into a Collins glass filled with fresh ice and top with prosecco. Garnish with a lemon twist. Yields 1 cocktail.
* Sumac Syrup: In a small saucepan, combine 1 cup granulated sugar, 1 cup water, ½ cup dried sumac berries, simmer for 30 minutes. Remove from heat, cool for 30 minutes. Fine-strain into a clean bottle and refrigerate up to 1 week.