Combine flour, cornmeal, sugar, baking powder, and salt in a food processor; pulse several times. Add butter; process until mixture is the consistency of coarse meal, about 7 seconds. With motor running, add yolks and enough ice water so dough comes together. Do not overmix.
Divide dough in half. Place each half on an 8x12-inch sheet of parchment paper. Roll in parchment to form a log 1 ¼-inches in diameter. Refrigerate logs until cold and firm, at least 1 hour or overnight.
Preheat oven to 350° F. Remove parchment paper from dough, and cut into ¼-inch-thick rounds. Space rounds 1 inch apart on baking sheets lined with silpats or parchment paper. Bake cookies until barely golden, about 10 minutes.
Carefully remove cookie trays from oven and place tray with cookies on it on a wire rack to cool. The cookies will continue to cook a little and harden up. Once cookies have cooled slightly 3-5 minutes, transfer cookies to wire racks to cool completely.
While cookies are cooling, make icing by combining lemon juice and powdered sugar, stirring well with a whisk or fork.
Once cookies have cooled, drizzle lemon icing over the top. Store cookies in an airtight container.
Notes
I didn’t count the cookies after I baked them because we baked them up a few batches at a time, but I think there were about 40 cookies total.Adapted from Martha Stewart