In a mixing bowl, combine flour, powdered sugar, and salt. Cut in butter until resembling coarse crumbs. Chill for 30 minutes. Roll out, cut circles for mini tart pan, prick with fork, chill 15 minutes, then bake at 350°F for 15-20 minutes.

In a saucepan, whisk lemon juice, sugar, eggs, zest, and vanilla. Cook over medium heat, stirring until thickened (7-10 minutes). Cool for 5 minutes, then fill cooled tart shells.

In a mixing bowl, beat egg whites on medium until soft peaks form. Gradually add sugar, beating until stiff peaks form (3-5 minutes). Fold in food coloring.

Transfer meringue to piping bag and pipe over lemon filling. Toast under broiler for 1-2 minutes until meringue is golden.

Arrange tarts on a platter and garnish with fresh mint leaves. Serve chilled.