Preheat the oven to 200 degrees and prepare 2 baking sheets with parchment paper. 

In a medium sized bowl or in your stand mixer, add the egg whites, cream of tartar and salt. Beat on high with your whisk attachment until soft peaks form.  When you remove the beater the peaks will be soft and will melt back into themselves. 

With the mixer still running, add the sugar to the mixture 2 tablespoons at a time,  beating until the sugar is completely dissolved. When the sugar has dissolved and the meringue forms stiff, glossy peaks when the beater is lifted turn off the mixer and gently fold in the lemon zest.

Spoon the meringue into a pastry bag with an open star tip. Pipe into 1 1/2 inch stars an inch or two apart on the baking sheet. You should be able to pipe around 50 stars from the meringue batter.

Bake the meringues for 90 minutes. Switching the baking sheets between the upper and lower oven racks halfway through the bake time. Then turn off the oven, leaving the meringues inside to dry completely for 1 hour. 

Remove to a wire baking rack and cool completely. Store the meringues in an airtight container for up to a month. Or freeze for up to 3 months.