Preheat oven to 350 degrees.
Put the fruit in a 13 x 9 baking pan. Sprinkle on 1/2 cup of the sugar and the corn starch and stir to mix.
In a mixing bowl, cream the butter and sugar. Add in flour, salt, baking powder and milk.
Spoon the batter over top of the fruit, using a spatula to smooth it out.
Sprinkle a little bit of raw sugar on top, if using. Bake for 40-45 minutes, or until light golden.