Start by making the ice cream. Whisk together the zest, lemon juice and sugar and salt in a medium, nonreactive bowl and refrigerate for at least 2 hours.

Place egg yolks in a large bowl and set aside. Heat the milk in a large saucepan over medium heat until it just begins to boil. Remove from heat and gradually whisk into egg yolks. Pour egg/milk mixture back into the saucepan and place over medium-low heat. Cook, stirring constantly, until the mixture is thick enough to coat the back of a spoon. Strain mixture and refrigerate for at least 2 hours, or until completely chilled.

Combine lemon mixture, custard and heavy cream and stir thoroughly. Freeze in an ice cream maker according to manufacturer’s directions. Allow to freeze overnight to harden.

To make the granita and sauce, purée raspberries in a food processor until just smooth. Transfer to a fine mesh strainer set over a medium bowl. Strain raspberries, using a rubber spatula to extract as much liquid as possible. Transfer ⅓ cup of purée to a small bowl and add 2 tablespoons sugar. Stir to combine. Cover and chill.

In a small saucepan set over medium-high heat, combine the water and remaining sugar and cook just until sugar dissolves. Set aside to cool.

Stir sugar mixture into remaining purée and place into an 8- by 8-inch glass dish. Freeze until mixture begins to set, stirring every 45 minutes for 2 to 3 hours. Cover and freeze until firm, about 6 hours. Sauce and granita can be made 1 day in advance. Once frozen, use a fork to scrape surface of the granita to form crystals.

To serve, place 1 scoop of ice cream into each of 2 dessert glasses.  Top each with 1 scoop of granita and drizzle with raspberry sauce.  Repeat for a total of 2 scoops ice cream and 2 scoops granita.  Serve immediately.