Pre-heat oven to 350° F
Mix the fruit with the sugar and corn starch.
Place in a 9 inch by 11 inch baking dish (or any size vessel that fits).
Mix the flour, sugar, baking powder and salt together in a bowl.
Add the butter.
Mix the butter with the dry ingredients until pea sized granules appear.
Stir in the buttermilk until a thick batter is formed.
Spoon the batter over the fruit.
Sprinkle with coarse sugar if desired.
Bake for 50-60 minutes.
Remove from oven and serve at room temperature.