• Preheat the oven to 350°F. Line 24 muffin tins with Reynolds cupcake liners.
• In a large bowl, whisk together the flour, baking powder, baking soda and salt. Set aside.
• In another bowl, mix together the milk and the vanilla.
• In the bowl of a stand mixer, cream together the butter and the sugar until light and fluffy. Add in the eggs, one at a time, mixing well between each addition. Add in one-third of the flour mixture and beat just until combined. Add half of the milk mixture, then another third of the flour mixture, mixing between additions. Add in the remaining milk mixture, followed by the remaining flour mixture. Mix just until combined. Fold in the poppyseeds.
• Fill the cupcake liners 2/3 full. Bake in the preheated oven until a toothpick inserted in the center comes out clean, 13-15 minutes. Let cool completely on a wire rack.

When the cupcakes are cool, make the frosting:

• In the bowl of a stand mixer, beat the egg whites until stiff peaks have formed.
• While the eggs are beating, combine the sugar and corn syrup in a small saucepan. Cook over medium heat. Once the mixture comes to a boil, remove from the heat and add the lemon extract and lemon zest.
• While the mixer is running, stream in the hot sugar mixture. Let the mixture beat until it forms a shiny, smooth marshmallow frosting, about 7-10 minutes. Do not scrape the sides, as sugar crystals will form. Beat in the food coloring, if desired.
• Add the frosting to a piping bag and pipe the frosting on top of the cooled cupcakes.