Preheat oven to 350 degrees F and oil the bottom and sides of a 8×11 pan, cut a piece of parchment paper to fit the bottom of pan, place in pan and oil the parchment.
In a large bowl mix together flour, sugar, baking powder, soda and salt with a whisk to remove lumps.
Add in the milk, applesauce, vanilla, lemon juice and zest, mix until well combined.
Fold in the blueberries and pour into prepared pan. Bake for 25 to 30 minutes or until a toothpick inserted into center comes out clean.
While bread is baking prepare the sauce by placing berries, water, maple syrup or agave, lemon juice and zest in a medium saucepan and bring to a boil. Reduce heat to simmer and cook 15 to 20 minutes or until blueberries burst and sauce thickens.
Allow to cool slightly, transfer to blender bowl and blend until completely smooth and pour into serving dish.
Slice bread, drizzle with blueberry sauce and serve.
Store leftover bread and sauce in airtight container in the fridge.