Pour heavy whipping cream into a large bowl and add sugar. Whip until medium peaks form and cream begins to thicken but is still smooth.
In a 9 inch springform pan, break just enough graham crackers to line the bottom of the pan. Add half of the whipped cream mixture on top of the graham crackers. Then add 1 pint of Talenti Key Lime Pie Gelato and smooth together. Repeat.
Zest one lime on top of cake, then freeze for 4 hours, until solid.
To make the raspberry coulis, add raspberries, sugar, and water to a food processor and blend together until smooth. Strain through a sieve and pour on top of icebox cake.