1. Cookie Dough: Preheat oven to 325°F (170?C). Line 2 baking sheets with parchment paper or silicone baking mats. Sift together flour, corn starch, baking powder and salt; set aside.
2. In bowl of stand mixer, beat sugar and butter until pale and fluffy. Mix in egg, lemon zest and vanilla. Mix in flour mixture in 2 additions. Divide dough into 2 portions and shape into disks; wrap each disk in plastic wrap. Refrigerate for at least 20 minutes or up to 2 days.
3. On lightly floured work surface, roll out dough into 1/4-inch (5 mm) thickness. Using 3-inch (8 cm) heart cutter, cut out 24 hearts, rerolling scraps once. Place on prepared baking sheets, about 2 inches (5 cm) apart. Refrigerate cookies for 10 minutes.
4. Bake one sheet at a time in center of oven for 8 to 10 minutes or until bottoms of cookies are lightly golden and tops are set. Let cool completely on rack.
5. Egg-Free Royal Icing: Place icing sugar in large mixing bowl. On low speed, gradually beat in 2 tbsp. (30 mL) water until blended. Beat in corn syrup and almond extract until smooth (if icing is too thick, add enough of the remaining water, 1 tsp/5 mL at a time).
6. Divide icing evenly among 3 bowls. Add pink food colouring to one bowl and red food colouring to another bowl. Leave the third bowl as is.
7. Add pink, red and white icing to piping bag fitted with small round tip. Pipe edges of cookies with desired icing colour; fill center of cookies with desired icing colour. Decorate with assorted sprinkles, dragées and/or sanding sugar.

Tip: Alternatively, instead of icing cookies, simply sprinkle with sugar before baking.