Instructions: Preparation: Preheat oven to 350°F (175°C). Grease and flour a 9x13-inch baking pan.
Prepare Grape Pie Filling: In a saucepan, combine halved grapes, granulated sugar, cornstarch, and lemon juice.
Make Cake Batter: In a large mixing bowl, whisk together flour, granulated sugar, brown sugar, baking powder, baking soda, and salt.
Assemble Cake: Spread half of the cake batter into prepared baking pan. Spoon cooled Grape Pie Filling evenly over batter.
Bake: Bake in preheated oven for 40-45 minutes, until golden brown and a toothpick inserted into the center comes out clean.
Cool and Serve: Allow Grape Pie Cake to cool slightly before serving. Serve warm or at room temperature.