Preheat oven to 176C | 350F. Grease a square 8x8-inch baking tray with cooking oil spray.
In a bowl, whisk brown sugar, butter and apple sauce/yoghurt until light and fluffy. Add sweetener/sugar, egg and vanilla.
In a smaller bowl, combine flour, baking powder, cinnamon and salt. Gradually beat in the dry ingredients.
Pour the water into the batter, and mix well. Do not over beat batter!
Pour batter into prepared baking tray and sprinkle with cinnamon sugar and chocolate chunks.
Swirl the cinnamon sugar and chocolate around to create a ripple effect. (Optional: Sprinkle with extra cinnamon sugar)
Bake until golden, 20 - 30 minutes, or until a toothpick inserted into the centre of the blondies comes out semi-dirty (The dirtier, the fudgy-er they will be). Be careful not to over-bake as they will dry out!
Cool completely before cutting into 16 bars.