In a medium-sized saucepan over medium heat bring blueberries, apples, sugar and water to a boil. Lower heat and simmer, stirring occasionally, until blueberries have released their juices, and apples are tender, about 15 minutes.
In a small bowl blend the cornstarch and 1 tablespoon + 1 teaspoon water. Stir it into the blueberry apple mixture and cook until it thickens about 1 minute. Remove from heat and cool to room temperature.
Butter a 9-inch spring form pan and line the bottom with parchment paper. Preheat oven to 350 degrees F.
Meanwhile in a large mixing bowl whisk together the flour and 3/4 cup of the sugar. (You can also do this in a food processor to make the next step easier.)
Cut in the butter with a pastry blender or pulse in a food processor until the mixture resembles coarse crumbs. Remove 1/2 cup of this mixture and set it to the side.
If you used a food processor dump the flour mixture out into a large mixing bowl. Stir in the baking powder, baking soda, salt and lemon zest.
In a separate bowl mix the yogurt, vanilla, and 1 egg until blended. Stir this wet mixture into the dry just until incorporated.
Spread the batter out in the prepared pan - it will be very thick.
In a bowl or in the food processor (no need to wash it out from earlier) beat on high speed (or whirl) the cream cheese, with the remaining 1/4 cup sugar, 1 egg and the lemon juice until smooth and creamy. Pour over the batter in the pan.
Gently drop half of the blueberry mixture over the cream cheese mixture by the spoonfuls leaving about a 1 - 2 inch border around the edge.
Stir the walnuts into the reserved flour mixture and sprinkle over the outside edge of the cake making a 1 - 2 inch border. Spoon the rest of the blueberries and apples into the middle.
Bake 40-50 minutes until center of cake barely jiggles when pan is gently shaken and top of the cake is golden brown.
Cool on wire rack 15 minutes then remove the rim of the pan.
Mix glaze ingredients in small bowl until smooth, Drizzle over cake. Enjoy
