Preheat the oven to 350 degrees. Process the flour, brown sugar, nuts, butter, and salt in a food processor until finely ground. Press into a greased aluminum foil-lined 13-9 inch baking dish.
Bake for 20 minutes or until golden. Cool on a wire rack.
Heat 3/4 cup granulated sugar and 1/2 cup of the lime juice over low heat, stirring until the sugar dissolves. Remove from the heat, and set aside.
Sprinkle the gelatin over the remaining 2 tablespoons lime juice in a medium bowl; stir gelatin mixture, and let stand 3-5 minutes.
Add the hot mixture to the gelatin mixture, stirring until the gelatin dissolves. Whisk in the sweetened condensed milk and 1 teaspoon lime zest.
Place the bowl inside of a larger bowl filled with ice; whisk mixture 10 minutes or until partially set.
Fold in the whipped cream. Pour evenly over the prepared crust; cover and chill 8 hours. Cut into diamond shapes. Garnish with lime zest, if desired.