Preheat oven to 350 degrees F or 176 degrees C
In a 9” by 9” baking pan, combine melted butter and brown sugar. Spread evenly over the bottom of the pan.
Spread the blueberries over the brown sugar and butter and sprinkle them with the lemon juice.
In a mixing bowl, cream the butter and sugar together mixing well. Add egg and vanilla.
Add baking powder, salt and cinnamon and continue to cream together.
Slowly add half the flour and mix well. Add milk while continuing to mix and add the rest of the flour.
Spread batter over the blueberries
Bake for 45-50 minutes or until a toothpick stuck into the middle of the cake comes out clean.