Apple Crumble

Ingredients

• 2 tablespoons cornstarch
• 1 teaspoon pure vanilla extract
• 1 tablespoon lemon juice
• 1 teaspoon ground cinnamon
• 1 teaspoon fine sea salt
• 1 cup old-fashioned oats
• 1/2 cup white granulated sugar
• 2 teaspoons ground cinnamon
• 1 cup light or dark brown sugar
• 2 pounds apples
• 1 cup white, all-purpose flour
• 3/4 cup unsalted butter