Blueberry Crumb Bars

Ingredients

• 1 stick unsalted butter melted
• 1 cup all-purpose flour
• 3/4 cup old-fashioned oats
• 1/2 cup sugar
• 1/4 cup light brown sugar packed
• 1 pinch salt
• 2 cups frozen blueberries
• 1/3 cup sugar
• 2 Tbsp lemon juice
• 2 tsp cornstarch
• 1 tsp lemon zest
• 1 granny smith apple