Ingredients Topping 1/2 cup (70g) all-purpose flour 1/2 cup old fashioned oats 1/2 cup (110g) packed light-brown sugar 1/2 tsp baking powder 1/4 tsp ground cinnamon 1/4 tsp salt 1/3 cup (76g) unsalted butter , diced into small cubes Apple filling 2 lbs Granny Smith apples (at room temperature) peeled, cored and sliced thin (about 1/8-inch) 3 Tbsp (42g) unsalted butter , melted 2 Tbsp all-purpose flour 3 Tbsp water 1 Tbsp lemon juice 1/2 tsp vanilla extract 1/4 cup (55g) light-brown sugar 1/2 tsp ground cinnamon 1 pinch salt Instructions Preheat oven to 375 degrees and position oven rack one level below the center. Butter an 8 by 8 inch baking dish (or small casserole dish with a similar size), set aside. In a mixing bowl whisk together 1/2 cup flour, the oats, 1/2 cup brown sugar, the baking powder, 1/4 tsp cinnamon and 1/4 tsp salt for 30 seconds. Add diced butter and using clean fingertips,...