Preheat the oven. Heat the oven to 350°F.

Prep the apples. Meanwhile, peel and core the apples. Slice the apples into thin wedges.

Prepare the pan and add the apples. Put the 1/4 cup of butter in a 9-inch square pan. Put it in the oven until the butter has melted. Remove the pan from the oven and sprinkle the butter with 1/2 cup of brown sugar. Arrange apple slices evenly over the butter and brown sugar layer.

Make the batter. Combine the 2 cups of flour, 1 cup of granulated sugar, 1 tablespoon of baking powder, 1 teaspoon of salt, 5 tablespoons of softened butter, 1 cup of milk, and the egg in a large mixing bowl. Beat on low speed with an electric mixer until combined. Increase to medium speed and beat for about 2 minutes longer. Scrape the sides of the bowl occasionally. Spoon the batter evenly over the apples and then gently spread to cover.

Make the streusel topping. In a medium bowl, combine 1/2 cup of brown sugar with the pecans, 1/4 cup of flour, and 1/2 teaspoon of cinnamon. Mix the 3 tablespoons of softened butter with a fork or your fingers until crumbs form. Sprinkle the streusel mixture evenly over the top of the batter.

Bake the cake. Bake the apple upside-down cake in the preheated oven for about 45 to 50 minutes, or until a wooden toothpick or a cake tester inserted in the center comes out clean.Invert and serve. Immediately invert the cake onto a large plate, platter, or pan and let stand for a minute. Remove the baking pan. If any apples stick to the baking pan, scrape them out onto the cake.