In a large mixing bowl, whisk together the flour, cornstarch, sugar, baking powder, baking soda, and salt.
In a separate mixing bowl, whisk together the milk, pineapple juice, yogurt, oil, melted butter, vanilla, and vinegar.
Pour the wet ingredients into the dry and carefully mix together until no more dry lumps, but don't over mix the batter.
Pour the batter over the pineapples and cherries in the cake tin. Smooth the top and place in the oven. Bake for 50 minutes until a skewer entered into the middle comes out clean. Be carefully not to push it all the way down because it can hit the fruit and come out wet even if the cake is cooked.
Let the cake cool for 15 minutes in the cake tin, then run a knife along the edge and turn onto a plate. The bottom is now the top.
Let cool at room temperature for a couple hours before serving.