Filling  

• ½ teaspoon cornstarch
• 4 teaspoons fresh lemon juice
• 1 ½ pounds Granny Smith apples (about 3 medium), peeled and cut into ½-inch cubes (about 4 cups)
• 1 ½ pounds Golden Delicious apples (about 3 medium), peeled and cut into ½-inch cubes (about 4 cups)
• 2/3cup granulated sugar
• Pinch table salt
• Pinch ground cinnamon
• Pinch ground nutmeg

Topping:

• ¾ cup dry quick-cooking oats
• ¼ cup packed light brown sugar
• 1 tbsp all-purpose flour
• 3 tbsp light butter, melted (such as Land O Lakes)
• ¼ cup chopped walnuts or pecans
• ½ tsp salt

Oven at 350 degrees, cook for ~55-60 minutes or until it starts to turn brown.