You can use any type of grapefruit for this recipe, but pink grapefruits make the most beautiful granita. If you opt for the grenadine, it also heightens the granita’s color. For the best results, squeeze your own grapefruit juice or buy it fresh and unpasteurized from a juice bar or market.
3/4 cup (6 oz./185 g) sugar
2 tsp. grated grapefruit zest
2 tsp. grenadine (optional)
1 1/2 cups (12 fl. oz./375 ml) unsweetened grapefruit juice
In a small saucepan, stir together the sugar, 3/4 cup (6 fl. oz./180 ml) water, and the grapefruit zest. Place over medium-high heat and bring to a steady boil. Boil, stirring frequently, until the syrup is clear with no visible grains of sugar, 1 to 2 minutes. Remove from the heat, pour into a bowl, and let cool to room temperature, about 20 minutes.
Cover the bowl with plastic wrap and refrigerate until the syrup is very cold, about 1 hour.
If desired, pour the chilled grapefruit syrup through a fine-mesh sieve into a bowl to strain out the zest, pressing hard on the zest with the back of a spoon to extract as much flavor as possible. Stir in the grenadine, if using, then add the grapefruit juice and stir well.
Pour the mixture into a shallow metal baking pan. Place in the freezer and freeze, whisking every 30 minutes, until semifirm, about 3 hours. Cover with plastic wrap and return to the freezer without stirring until frozen solid, at least 8 hours or up to 24 hours.
At least 1 hour before serving, place 4 glasses in the freezer. To serve, using a fork, scrape the surface of the granita into fine ice crystals. Scoop the granita into the frozen glasses. Serve immediately. Serves 4 to 6.
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