In a large bowl, beat butter, cream cheese, and confectioners’ sugar with a mixer at medium-high speed until fluffy, 3 to 4 minutes, stopping to scrape sides of bowl.
In a medium bowl, whisk together flour, cornstarch, poppy seeds, 1½ teaspoons zest, and salt. With mixer on low speed, gradually add flour mixture to butter mixture, beating until combined. Beat in lime juice and vanilla. Divide dough in half. Roll each half into a 10-inch log. Wrap tightly in plastic wrap, and refrigerate for at least 2 hours or up to 3 days.
Preheat oven to 350°. Line baking sheets with parchment paper.
Cut logs into ¼-inch-thick slices. Place slices at least 1 inch apart on prepared pans.
Bake until edges are lightly browned, 8 to 10 minutes. Let cool on pans for 5 minutes. Remove from pans, and let cool completely on wire racks.
Spoon ½ to 1 teaspoon Coconut Lime Glaze onto each cookie. Garnish with zest, if desired. Let stand until glaze is set, about 1 hour. Refrigerate in airtight containers for up to 5 days.
Recipe by Taste of the South at https://tasteofthesouthmagazine.com/key-lime-meltaway-cookies/