Apple and Blueberry Crisp

1 Apple, any kind except red delicious
2 teaspoons fresh lemon juice
1 pint blueberries
1/2 cup sugar
3 teaspoons corn starch
1 tablespoon butter cut into small pieces
1/2 cup all-purpose flour
1/2 cup sugar
1/2 stick (4 tablespoons) cold butter
1/2 teaspoon ground cinnamon
1/8 teaspoon salt
1 tablespoon Turbinado sugar (optional)

Preheat oven to 350°.
Peel apple and cut into small pieces. Put them in a medium size bowl. Add lemon juice and mix. Add blueberries, sugar, corn starch and butter. Mix well and transfer this mixture into 8×8 inch Pyrex dish. Distribute the fruit mixture in the dish
In another bowl mix flour, sugar, butter, cinnamon and salt. (If the flour mixture is too dry add one more tablespoon butter.) Spread this mixture on top of the  fruits evenly.
Sprinkle Turbinado sugar if using on top and bake for 35 minutes on 350°.
Cut into 9 squares and serve with ice cream or whipping cream. Serve hot or cold.
Note: It may be juicy when it is hot. But it will become thick when it is warm.