01 - Preheat oven to 350°F (175°C). Grease and flour a 9x13-inch baking pan.
02 - In a medium bowl, whisk together flour, baking powder, baking soda, and salt.
03 - In a large bowl, cream softened butter and granulated sugar until light and fluffy. Beat in eggs one at a time, then stir in vanilla extract.
04 - Alternately add the flour mixture and cherry soda to the butter mixture, beginning and ending with the flour mixture. Mix until just combined.
05 - Stir in the whole milk and chopped maraschino cherries.
06 - Pour batter into the prepared pan and smooth the top. Bake for 30–35 minutes, or until a toothpick inserted into the center comes out clean.
07 - While the cake bakes, combine ½ cup cherry soda and ¼ cup granulated sugar in a small saucepan. Bring to a simmer over medium heat, stirring until sugar dissolves. Simmer for 2–3 minutes to slightly thicken. Remove from heat and allow to cool.
08 - Once the cake is baked, let it cool for 10 minutes. Poke holes all over the surface of the cake using a skewer or fork. Pour the cooled cherry syrup evenly over the cake. Allow to cool completely.
09 - In a separate bowl, beat heavy cream, powdered sugar, and vanilla extract until stiff peaks form.
10 - Spread the whipped topping evenly over the cooled cake. Garnish with additional maraschino cherries.
11 - Refrigerate the assembled cake for at least 1 hour before serving for optimal flavor.