Place an oven rack in the center of the oven. Preheat the oven to 200 degrees F. Line a baking sheet with parchment paper. Set aside.
Using an electric mixer, beat egg whites and salt on medium-high speed until foamy, about 1 minute. With mixer running, gradually add sugar in 2 additions beating for 3 minutes between each addition. Beat until firm peaks form, about 2 minutes longer.
With a spatula fold in the lime zest. Drop about 3 tablespoons of the mixture onto the prepared baking sheet about 2 inches apart. Bake for 30 minutes.
Rotate the pan and bake for another 30 minutes. Turn off the oven and allow the meringues to cool completely while still in the oven, about 2 hours.