Preheat the oven to 350°F (175°C). Grease a 9 x 13-inch (23 x 33 cm) baking dish preferably with butter or nonstick cooking spray.
Place the sliced apples in a large microwave-safe bowl. Cover and microwave for 3–4 minutes, until the apples have begun to soften and release some of their juices but aren't fully tender.
3½ lbs (1.6 kg) Granny Smith apples
Add the butter, brown sugar, cinnamon, allspice, lemon juice and cornstarch to the apples. Stir until the apples are evenly coated, then cover and microwave for another 2–3 minutes, until the juices have begun to thicken. Transfer the apple filling and its juices to the prepared baking dish and spread evenly. Allow the filling to cool slightly while preparing the cake batter.
2 tbsps (28 g) salted butter, ½ cup (100 g) packed light brown sugar, 1 tsp (2.5 g) ground cinnamon, ¼ tsp (0.5 g) ground allspice, 2 tbsps (30 ml) fresh lemon juice, 2 tsps (5 g) cornstarch
Beat the softened butter and granulated sugar in a large bowl until smooth and creamy. Add the eggs one at a time, mixing well after each addition, then mix in the vanilla extract.
¾ cup (170 g) salted butter, 1 cup (200 g) granulated sugar, 2 large eggs, 1 tsp (5 ml) vanilla extract
Whisk together the flour and baking powder in a separate bowl. Gradually add the dry ingredients to the butter mixture, mixing only until no dry flour remains. The cake batter will be thick and spreadable.
1¾ cups (219 g) all-purpose flour, 1½ tsps (6 g) baking powder
Spoon the cake batter in portions over the slightly cooled apple filling, then use a spatula to carefully spread it across the surface. The batter does not need to completely cover the apples. Sprinkle the turbinado sugar evenly over the cake batter.
2 tbsps (25 g) turbinado sugar
Bake for 50–55 minutes, until the cake topping is golden brown and baked through. Check for doneness by inserting a toothpick into a thicker area of the cake topping without pushing it down into the apple filling; it should come out clean or with a few moist cake crumbs.
Allow the apple cake cobbler to cool for at least 10 minutes before serving. The apple filling will be saucier while the cobbler is very warm and will continue to thicken as it cools. Serve warm with vanilla ice cream or whipped cream, if desired.
vanilla ice cream, whipped cream