Preheat oven to 350°. Spray a cast-iron wedge pan with baking spray with flour.
For cookies:
In a large bowl, beat butter and brown sugar with a mixer at medium speed until fluffy, 2 to 3 minutes, stopping to scrape sides of bowl. Add egg, beating well. Beat in zest.
In a medium bowl, whisk together flour, poppy seeds, baking powder, and salt. With mixer on low speed, gradually add flour mixture to butter mixture, beating until combined. Press about 3 tablespoons dough into each well of pan.
Bake until tops are golden brown, 15 to 18 minutes. Let cool in pan on a wire rack for 5 minutes. Remove from pan, and let cool completely on a wire rack.
For glaze:
In a medium bowl, whisk together all ingredients until smooth; drizzle onto cooled cookies. Garnish with zest and poppy seeds, if desired. Store in an airtight container for up to 3 days.
Recipe by Southern Cast Iron at https://southerncastiron.com/meyer-lemon-poppy-seed-cookies/