1Grease and flour a 10x2" round tart pan with a removable bottom, or a 11x7x1-1/2" baking pan.
2For filling, in a small saucepan, stir together UNDRAINED berries and the cornstarch until well combined.
Cook and stir until tickened and bubbly.
Remove from heat.
sieve the mixture to remove any seeds.
Set filling aside to cool slightly.
3In a large mixing bowl, stir together flour and sugar.
Using a pastry blender, cut in butter tillmixture resembles coarse crumbs.
Set 1/2 CUP of this mixture aside for crumb topping.
4Into the remaining flour mixture, stir in baking powder, baking soda, and sale.
Make a well in the center to add the next step.
5In a small bowl, combine egg and buttermilk.
Add the egg mixture all at once to the dry mixture.
Stir until JUST MOISTENED.
6Spread TWO-THIRDS of the batter over the bottom and about 1" up the sides of the prepared pan.
Carefully spread the fruit filling over the top of the batter in the pan.
Spoon the remaining batter in small mounds on top of the entire surface.
Sprinkle with the crumb topping.
7Bake in 350 oven for 30-35 minutes or until a wooden toothpick inserted near center comes out clean.
Cool in pan on a rack for 15 minutes.
Remove coffee cake from tart pan (however, leave it IN the baking pan if that is what you are using).
Cut into wedges or squares.