1 cup (2 sticks) unsalted butter, room temperature
3/4 cup granulated sugar
1 large egg
1 1/4 teaspoons pure vanilla extract
1/2 cup confectioners' sugar
1 to 2 drops red or pink food coloring
Preheat oven to 400 F degrees. In a medium bowl, whisk together flour, cornmeal, and salt. In a large bowl, using an electric mixer, beat butter and 1/2 cup granulated sugar on medium-high until creamy, 3 minutes. Add egg and 1 teaspoon vanilla and beat until combined. With mixer on low, gradually add flour mixture and beat to combine.
Place 1/4 cup granulated sugar in a small bowl; roll dough into 1-inch balls and coat with sugar. Transfer to two parchment-lined baking sheets. With the bottom of a glass, flatten balls to 1 1/2 inches in diameter. Press a 1-inch heart-shaped cookie cutter into each (do not cut through). Bake until cookies are golden at edges, 10 minutes, rotating sheets halfway through. Let cookies cool on wire racks.
In a small bowl, whisk together confectioners' sugar, 1/4 teaspoon vanilla, and 1 3/4 teaspoons cold water. Whisk in food coloring. With a small spoon, spread glaze inside heart. Let set 15 minutes.