01 - Preheat oven to 350°F. Line an 8x8-inch baking pan with parchment paper, allowing an overhang for easy removal.
02 - In a medium mixing bowl, whisk together all-purpose flour, baking powder, fine sea salt, and ground cinnamon until evenly blended.
03 - In a large mixing bowl, whisk melted butter, light brown sugar, and granulated sugar until smooth. Add egg and vanilla extract; mix until fully incorporated.
04 - Stir apple butter into the wet mixture until thoroughly combined.
05 - Fold the dry ingredients into the wet mixture just until no streaks of flour remain; avoid overmixing.
06 - Transfer batter to the prepared pan, smoothing the top for even thickness.
07 - In a small bowl, mix granulated sugar with ground cinnamon. Sprinkle evenly over the batter.
08 - Bake for 28 to 32 minutes, or until the center is set and a toothpick inserted comes out with only a few moist crumbs.
09 - Allow blondies to cool completely in the pan before lifting out and slicing into 16 squares.