Preheat oven to 350°F (175°C).

Coat a 9 x 5 x 3-inch loaf pan with nonstick spray.

Prepare the streusel: In a medium bowl, stir together 1 cup all-purpose flour, 1/2 cup packed light-brown sugar, 1/2 cup melted butter, and 2 teaspoons ground cinnamon until crumbly.

Set the streusel aside.

Prepare the cake: In a large bowl, stir together 2 cups all-purpose flour, 3/4 cup granulated sugar, 2 teaspoons baking powder, and 1/2 teaspoon salt.

In a medium bowl, beat 2 large eggs with a fork until blended.

Stir in 1/2 cup melted butter and 1/2 cup 1% low-fat milk to combine.

Add the wet ingredients to the dry ingredients and fold with a rubber spatula just until dry ingredients are moistened.

Spoon half of the batter into the prepared pan; spread to cover the bottom.

Sprinkle with half of the diced granny smith apples (about 2 medium apples, peeled, halved, cored, and cut into 1/2-inch dice).

Sprinkle with half of the streusel.

Spoon the remaining batter into the pan, spreading to cover.

Sprinkle with the remaining streusel, then the remaining apples, and finally the remaining streusel.

Bake for 1 hour 10 minutes to 1 hour 20 minutes, or until a wooden pick inserted into the center comes out clean.

Cool in the pan on a wire rack for 10 minutes.

Run a knife around the sides of the pan to loosen the cake.

Invert the cake onto the wire rack.

Turn the streusel side up and let cool completely before slicing and serving.