Preheat oven to 350° and spray an 11 x 7 or a 2.5 quart baking dish with a non stick spray. Set aside.
In a small bowl, add blueberries and top with lemon juice and zest. Stir and add to baking dish.
In a medium bowl, add flour, sugar, baking powder, butter, vanilla, cinnamon, salt, and milk. Mix well.
Boil 1 cup of water and then add corn starch and sugar to water. Stir vigorously until dissolved.
Bake for 50-60 minutes or until browned.
Recipe adapted from The Southern Lady Cooks