3 cups fresh blueberries

1/4 cup (50 g) granulated sugar

1 tablespoon cornstarch

1 tablespoon fresh lemon juice

Zest of 1 lemon (optional, or substitute with a pinch of cinnamon)

3/4 cup (170 g) unsalted butter, room temperature

1/3 cup (66 g) granulated sugar

1/3 cup (66 g) light brown sugar, packed

2 teaspoons vanilla extract

2 cups (250 g) all-purpose flour, spooned and leveled

1/2 teaspoon baking powder

1/2 teaspoon salt

Powdered sugar, for dusting (optional)

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Preheat oven to 350°F (175°C) and line an 8×8-inch or 9×9-inch baking pan with parchment paper, leaving an overhang for easy removal.
In a medium bowl, toss together blueberries, 1/4 cup sugar, cornstarch, lemon juice, and lemon zest (or cinnamon). Set aside.
In a large mixing bowl, cream together butter, 1/3 cup sugar, 1/3 cup brown sugar, and vanilla until smooth and fluffy.
Add flour, baking powder, and salt. Mix until the dough forms coarse crumbs that hold together when pressed.
Press about two-thirds of the crumb mixture into the bottom of the prepared pan to form the crust.
Spread the blueberry mixture evenly over the crust, ensuring it reaches the edges.
Sprinkle the remaining crumb mixture over the blueberries, leaving some larger chunks for texture.
Bake for 40–45 minutes, or until the top is lightly golden and the blueberry filling is bubbling around the edges.
Let cool completely in the pan before lifting out and cutting into bars. Dust with powdered sugar if desired.

Let bars cool fully before slicing so the filling can set.

Use frozen blueberries directly from the freezer — no need to thaw.

Add nuts like almonds or pecans for crunch.

Double the recipe for a 9×13-inch pan; bake about 50–55 minutes.

Store covered at room temperature for 2 days or refrigerate for up to 5 days.