Preheat oven to 350 degrees.
Grease an 8x8 baking dish. I use cooking spray.
Place a saucepan on medium-high heat. Add the apples, cinnamon, vanilla, sweetener, and lemon juice. Stir and cook for 2-3 minutes until the apples are soft.
6 Granny smith green apples, 1 teaspoon fresh lemon juice, ½ cup sweetener, 1 teaspoon vanilla, 1 teaspoon cinnamon
Mix the cornstarch and water in a small bowl. Add to the pan and stir. Cook for 30 seconds.
1 tablespoon cornstarch, 1 tablespoon water
Transfer the apple mixture to the bottom of the baking dish.
Combine the oats, brown sweetener, cinnamon and melted butter in a separate bowl.
1 cup rolled oats, ¼ cup brown sweetener, ½ teaspoon cinnamon, 3 tablespoons melted butter
Spread the topping throughout the pan.
Bake for 20 minutes.
Loosely cover the pan with foil to prevent the topping from over-browning.
Bake for an additional 20-25 minutes until the apples are soft.
Cool before serving.