Bring the apple cider to a boil in a small saucepan. Reduce heat to medium-low and simmer until reduced to ¼ cup, about 15 to 20 minutes. Let cool slightly.
Melt the butter in a skillet over medium heat, stirring frequently, until golden brown and fragrant. Add the diced apple and cook 2 minutes. Transfer to a large mixing bowl and let cool about 5 minutes.
Heat the oven to 375°F. Line a 9x13-inch baking pan with parchment paper or coat with baking spray.
Whisk the brown sugar, eggs, reduced cider, and vanilla into the cooled brown butter and apple mixture until smooth.
Add the flour, baking powder, cinnamon, allspice, and salt. Fold with a spatula just until combined. Do not overmix.
Combine the granulated sugar and cinnamon in a small bowl. Stir in the turbinado sugar if using.
Spread the batter evenly into the prepared pan.
Sprinkle the cinnamon sugar topping evenly over the surface.
Bake 20 to 22 minutes, until the edges are set and golden and the center is just set. Do not overbake.
Let the blondies cool completely in the pan before lifting out and cutting into squares.