• 1 cup sugar
• Coarsely grated zest of 1 lime
• 3 large egg whites at room temperature
• Pinch of cream of tartar
• Pinch of salt
• ½ teaspoon pure vanilla extract
• Powdered sugar for dusting (optional)

Preheat the oven to 200°F. Line a large baking sheet with baking parchment or aluminum foil.

Combine the sugar, ⅓ cup water, and the lime zest in a heavy saucepan. Bring to a simmer over medium-high heat, occasionally swirling the pan by the handle, but not stirring. When the liquid turns from cloudy to clear, cover the pan and reduce the heat to low.

Meanwhile, with an electric mixer, beat the egg whites at low speed until they start to become foamy. Add the cream of tartar and salt, and gradually increase the speed and beat until the whites stand in soft peaks. Stir in the vanilla.

Remove the lid from the sugar syrup and boil over medium-high heat until the temperature on a candy thermometer reaches 238°F. and a few drops of syrup drizzled into a bowl of cold water holds a soft but definite shape. Slowly pour the hot syrup through a coarse strainer into the egg whites while beating at medium speed; discard the lime zest. Continue to beat until the meringue stands in stiff peaks and the outside of the mixer bowl is barely warm to the touch, about 10 minutes.

Using a pastry bag and a ½-inch cannelated tip or a teaspoon, pipe or spoon bite-size rounded mounds of meringue, with a little pointed top, about 1 inch apart on the baking parchment. Place the baking sheet on the middle rack of the oven. Keep the oven door slightly ajar and bake the meringues until they can be gently loosened from the parchment with a spatula, about 1 hour. Remove from the oven and let the meringues cool completely on the baking sheet. The finished besitos should be white, crisp, and light.