Directions

1. Preheat oven to 350. Process graham crackers and 2 tablespoons sugar in a food processor until fine crumbs form; add butter. Process until combined. Transfer mixture to a 9-inch tart pan with a removable bottom; pat into bottom and up sides. Place pan on a baking sheet, and bake until crust is fragrant and slightly colored, about 10 minutes.
2. Meanwhile, in a medium bowl, combine condensed milk, lime juice, egg yolks, remaining 1/2 cup sugar, and salt; whisk until smooth. Pour mixture into crust (warm or cool is fine), leaving 1/8 inch at the top; return to oven. Bake until filling is set around edge but still slightly loose in center, 20 to 25 minutes.
3. Cool completely at room temperature; then refrigerate until chilled, at least 2 hours. To store longer, cover and refrigerate, up to 2 days. Serve, garnished with zest, if desired.