Raspberry-Swirl Mini Bundt Cakes

If you don't have a mini sponge cake mold, you can bake one large sponge cake. If you have an 8-cup baking dish, this is ideal, but a 10-cup baking dish will also work (just the cake won't be as tall). Bake at 350 ° C for 25-28 minutes or until a wooden stick comes out clean. Spreading the batter evenly over the mini cakes can be a bit more difficult. Try to spoon the dough into a large zippered plastic bag; then cut off one bottom corner of the bag and pour the dough into the molds.
Combine the raspberries, 1/4 cup granulated sugar, and 1 tablespoon water in a small saucepan. Bring to a boil. Reduce the heat and simmer for 5 minutes or until the berries break apart and the mixture thickens slightly, stirring frequently. Put the cornstarch in a small bowl; add the remaining 1 tablespoon of water, stirring until smooth. Add the cornstarch mixture to the pan; cook for 1 minute or until thickened. Allow to cool completely.Preheat the oven to 350 degrees.Spoon flour into dry measuring cups; smooth with a knife. Combine the flour, baking powder, baking soda, and salt in a bowl, mixing well with a whisk.Put the butter and remaining 1 cup granulated sugar in a bowl; beat with a mixer on medium speed until fluffy (about 5 minutes). Whisk with vanilla. Add the eggs 1 at a time, beating thoroughly after each addition. Add the flour mixture and buttermilk alternately to the butter mixture, starting and ending with the flour mixture.Place approximately 2 tablespoons of batter on the bottom of each of the 12 mini cake cups smeared with baking spray, spreading them evenly. Evenly spread about 3 tablespoons of the raspberry mixture into each cup, spreading evenly over the dough. Spread the remaining dough evenly, flattening the tops with a spatula. Bake at 350 ° C for 20 minutes or until a wooden stick inserted in the middle comes out clean. Cool in the tins on a wire rack for 10 minutes; remove the cakes from the tins. Cool completely on a wire rack.Combine the powdered sugar and 2-3 teaspoons of water in a small bowl, stirring, until smooth. Drizzle the icing evenly over the cakes.Bake the second portionIt's best to prepare one serving of cupcakes at a time (don't double the amount of dough), although you can easily double the amount of raspberry mixture.