7 cups fresh or store bought pink grapefruit juice
2 cups packed light-brown sugar
1 vanilla bean, halved lengthwise
Pink sanding sugar, for glasses
12 ounces vodka
Cut away peel and pith from grapefruits. Cut each segment on both sides to free from membrane. Set segments aside.
Puree raspberries in a food processor. Press puree through a fine sieve into a bowl: discard seeds. Set aside
Put 1 cup grapefruit juice and the brown sugar into a large saucepan over medium heat. Scrape vanilla seeds from bean into pan with the tip of a paring knife; add bean to pan. Whisk until sugar has dissolved. Raise heat to medium-high. Add grapefruits; cook, stirring occasionally, until segments begin to turn golden brown, 4to 5 minutes. Remove from heat; whisk in raspberry puree. Pour through a fine sieve into a heatproof airtight container; discard solids. Let cool at room temperature. Refrigerate until cold (up to 3 days)
Dip the moistened rims of twelve 8 – ounce glasses in sanding sugar. For each cocktail, combine 2 ounces grapefruit-raspberry mixture, 4 ounces grapefruit juice and 1 ounce of vodka in a cocktail shaker; add ice. Shake 30 seconds; strain into a prepared glass.
For a non alcoholic version, omit the Vodka, and top each drink with pink-grapefruit soda or seltzer. For garnish, thread two grapefruit segments onto each of twelve drink picks, then place on a rimmed baking sheet wrapped tightly in plastic, and freeze. Top each glass with a frozen skewer and serve.