Preheat your oven to 350°F (175°C) and set the oven rack to the middle position.
Spray a 9-inch pie pan with nonstick cooking spray to prevent sticking.
In a food processor, combine 60 salted saltine crackers, 3 tablespoons granulated sugar, 8 tablespoons unsalted butter, and 1 teaspoon kosher salt. Pulse until the crackers become coarse crumbs (10-15 pulses).
Press the saltine crumbs firmly into an even layer covering the bottom and sides of the pie plate.
Transfer the pie plate to a baking sheet and bake the crust until golden brown (18-20 minutes).
In a large bowl, whisk together 14 ounces sweetened condensed milk, 4 large egg yolks, ¼ cup heavy cream, 1 tablespoon grated lemon and/or lime zest, and ¼ teaspoon kosher salt.
Add 9 tablespoons fresh-squeezed lemon and/or lime juice and whisk until fully incorporated.
Pour the filling mixture into the pre-baked saltine crust and set the pie on the center rack of the oven.
Bake the pie for about 16-18 minutes, until the filling has set.
Transfer the pie to a cooling rack and let it cool completely.
In a small bowl, whisk together 1 cup sour cream and ¼ cup granulated sugar until smooth. Spread this mixture evenly over the cooled pie.
Refrigerate the pie for at least 4 hours, or up to overnight, before serving.
