Blueberry Crumb Bars - Walter Stewart's Market

Ingredients

• 1 cup white sugar
• 1 teaspoon baking powder
• 3 cups all-purpose flour
• 1 cup cold unsalted butter (2 sticks or 8 ounces)
• 1 egg
• 1/4 teaspoon salt
• Zest and juice of one lemon
• 4 cups fresh blueberries
• 1/2 cup white sugar
• 4 teaspoons cornstarch