Preheat oven to 350°F. Line cookies sheets with parchment paper. Mix flour, baking soda, and salt in a bowl; set aside. Beat the butter and granulated sugar in a mixer on medium high until light and fluffy, about 3 minutes. Beat in egg. Alternately add the flour mixture, vanilla, and buttermilk, ending with the flour. Stir in lemon zest.
Drop dough by rounded teaspoonfuls onto cookie sheets (or use pastry bag with a 1/2 inch round tip). Bake 8 to 10 minutes, or until cookies are lightly golden. Cool completely on a wire rack.
For glaze, combine powdered sugar, corn syrup, lemon juice, and water; mix until smooth. Spoon half the glaze into a second bowl and stir in 2 to 3 drops red food coloring to tint pink. Mix 3 to 4 drops yellow food coloring in first bowl.
Turn cookies flat side up. Top with glazes using a spreader or a pastry bag. Let dry 30 minutes before storing.