Just like tomatoes in the summer, between December and April, the South grows dozens of different varieties of citrus from flamingo pink-fleshed grapefruits to golden lemons. Pick up these drops of sunshine at the grocery store or the farmers’ market any chance you get. This tart turns vibrant grapefruits into a delicious dessert that is a refreshing remedy for the midwinter blues. You will also want to grab a lemon for fresh lemon juice. This tart’s crunchy, slightly salty crust (made with saltine crackers) pairs beautifully with the tangy grapefruit filling and sweet whipped cream. If you do not have a mixer on hand, you can also use a whisk to prepare the whipped cream. Just whisk in a bowl and gradually add the powdered sugar.
Preheat oven to 325°F. Stir together cracker crumbs, 1/4 cup of the granulated sugar, and melted butter in a small bowl. Press mixture into a lightly greased 9-inch fluted tart pan with removable rim, pressing evenly up sides and on bottom.
Bake in preheated oven until crust is lightly browned, 12 to 14 minutes.
Meanwhile, combine cornstarch, salt, and remaining 1 1/4 cups granulated sugar in a medium-size heavy saucepan. Whisk in juices and egg yolks. Using a small wooden pick, stir in a small amount of deep pink food coloring gel. Cook over medium, whisking constantly, until mixture comes to a boil. Boil, whisking constantly, 1 minute. Remove from heat; whisk in 1/3 cup butter pieces.
Pour filling into prepared tart shell. Chill uncovered 4 to 24 hours.
Beat cream with an electric mixer at medium-high speed until foamy; gradually add powdered sugar, beating until soft peaks form. Dollop over tart. Top with quartered grapefruit slices.