01 -
Set your oven to 375°F to preheat. Put parchment paper on the bottom of your 9"x13" pan after spraying it with cooking spray.
02 -
Stir together the melted butter, both sugars, baking powder, flour, and cinnamon. Mix in the eggs and almond extract until smooth.
03 -
Save 1½ cups of the mixture for the topping. Press the rest into the pan you just prepared.
04 -
Combine the lemon juice, sugar, and cornstarch first, then carefully mix in the blackberries. Spread this over the pressed crust.
05 -
Scatter the reserved topping mixture over the blackberries. Put the pan in the oven and bake for about 40 to 45 minutes or until it turns golden. Let it cool fully before cutting.