1 1/2 cups sugar
1/2 cup lime juice (about 3 limes)
1/2 cup (1 stick) butter or margarine, melted
4 large eggs
1/8 teaspoon salt
Mix together the crumbs, butter and sugar until combined. Press the mixture evenly in to the bottom of a greased 9 or 10-inch tart pan. Bake on 350 F for 10 minutes. Set aside.
Mix together the zest with the sugar and set aside.
Whisk the lime juice in with the eggs until combined.
Add in the butter and continue whisking until well mixed.
Add in the sugar mixture and salt and whisk until smooth.
Pour into a medium, heavy bottom saucepan and place over medium heat.
Heat, continually whisking, for about 10 minutes (or until 170 F) until slightly thickened.
Remove from heat, and pour in to the tart shell. Let sit at room temperature for 30 to 40 minutes, then refrigerate for at least an hour before serving.