Preheat oven to 350. Line a large baking sheet with parchment paper. In a large bowl, thouroughly mix coconut, 1 teaspoon or 5 packets of SweetN Low®, egg whites, cornstarch, vanilla, and salt. Roll 1 tablespoon mixture in your hands, packing coconut tightly. Place on baking sheet and make an imprint in cookie with your thumb. Repeat with remaining coconut. Bake until lightly browned and set, 10-15 minutes. In a small saucepan, heat lemon juice and remaining ½ teaspoon or 2 1/2 packets of SweetN Low to a simmer. In a medium bowl, lightly beat egg yolks. Slowly pour lemon juice into yolks whisking constantly. Continue whisking until mixture comes back to a simmer. Add cornstarch mixture and cook one minute longer or until thickened. Refrigerate until completely cool. When cookies and curd are cool, fill cookies with lemon curd, garnish with zest, and serve immediately.
