Preheat oven to 350 degrees F. From lemon, grate 1 teaspoon zest and squeeze 3 tablespoons juice. In large bowl, whisk flour, baking powder and salt. With mixer on medium-high speed, beat granulated sugar, butter and lemon zest until creamy. Add ricotta, eggs and vanilla, beating until combined, stopping and scarping down side of bowl occasionally. Beat in flour mixture until just smooth. Line large cookie sheet with parchment paper. With small cookie scoop (about 2 teaspoons), scoop dough into balls; place on cookie sheet, spacing 1 1/2 inches apart. With fingers, pat each down into flat disk. Bake 15 to 20 minutes or until bottoms are golden brown. Let cool on cookie sheet 5 minutes. Transfer to wire rack to cool completely. Make glaze: In medium bowl, stir together confectioners' sugar, reserved lemon juice and 1/2 teaspoon water until smooth. Tint with food coloring to desired shade. Place in small plastic bag with one corner snipped off and drizzle all over cookies. Decorate with edible stars if desired. Let stand until set, about 30 minutes. Cookies can be stored in airtight containers in freezer for up to 1 month. Makes about 3 1/2 dozen. For the Chocolate-Glazed Ricotta variation: Omit lemon in cookies. Instead of confectioners' sugar glaze, drizzle with melted dark chocolate.