Heat the oven to 180 C (350 F). Mix together the cracker crumbs, the melted butter, and the cinnamon until well combined. Press into the bottom of a 9 inch pie pan and bake in the preheated oven for 7-8 minutes then remove and let the crust cool for at least 30 min before filling.
For the filling:
Whisk together the sweetened condensed milk, sour cream, lime juice, and lime zest until well combined. Pour into the crust and bake at 180 C (350F) for 10 minutes. Remove from the oven and chill on the counter for 30 minutes or so, then continue chilling in fridge.
For the sweetened whipped cream:
Beat heavy cream, icing sugar, and vanilla extract together with an electric mixer fitted with a whisk attachment on medium high speed for 2-3 minutes until stiff peaks form. Top the chilled pie with the whipped cream mix and garnish with extra lime slices and/or lime zest if desired.