Ingredients
3 c. all-purpose flour
1 tsp. salt
1 tsp. ground cinnamon
1 c. granulated sugar
2 sticks unsalted butter, cut into small pieces
1/2 c. granulated sugar
4 tsp. cornstarch
3 1/2 c. fresh blueberries
1/2 c. blueberry jam
2 tsp. lemon zest
2 tbsp. fresh lemon juice
Pinch of salt
Instructions
Preheat the oven to 375° with the rack positioned in the lower third of the oven. Spray a 9-by-13-inch baking pan with cooking spray. Line the pan with parchment paper.
To make the crust and topping: Whisk together the flour, salt, cinnamon, and sugar in a medium bowl until combined. Add the butter. Using a pastry blender or your fingertips, work the butter into the flour mixture until well combined and the mixture is the texture of wet sand (the mixture should hold together when squeezed). Press half of the mixture into the prepared pan in an even layer. Bake until lightly browned, about 15 minutes.
To make the filling: Whisk together the sugar and cornstarch in a medium bowl. Add the blueberries, jam, lemon zest and juice, and salt, tossing to combine. Spread the filling in an even layer over the warm crust in the pan.
Sprinkle the remaining crust mixture over the top of the blueberry filling in an even layer, leaving some larger clumps. Bake until golden brown on top and the filling is bubbly around the edges and in the center, about 1 hour. Remove from the oven and let cool completely in the pan on a wire rack, about 3 hours. Cut into bars and serve.