Blueberry Crumb Bars

Bahan-bahan (9 porsi)

• 1 cup sugar (plus extra 1/3 cup for blueberries)
• 1 tsp . baking powder
• 3 cups all-purpose flour
• 1 cup unsalted butter
• 1 egg
• 1 tsp . vanilla extract
• 1/2 tsp . salt
• zest of one lemon
• 4 cups fresh blueberries
• 3 Tbsp . cornstarch