For the streusel topping:
1/4 cup granulated sugar
1/2 cup all-purpose flour
1/4 cup brown sugar, packed
1 teaspoon ground cinnamon
1/4 cup unsalted butter, cold and cut into small pieces
For the loaf:
1/2 teaspoon salt
1 teaspoon ground cinnamon
1 1/2 cups all-purpose flour
1 teaspoon baking powder
1/2 teaspoon baking soda
1/2 teaspoon ground nutmeg
1/2 cup unsalted butter, softened
1/2 cup granulated sugar
1/2 cup brown sugar, packed
2 large eggs
1 teaspoon vanilla extract
1/2 cup sour cream or Greek yogurt
1 1/2 cups diced apples (about 2 medium apples), peeled
Preheat your oven to 350°F (175°C). Grease and flour a 9×5 inch loaf pan.
Make the streusel topping: In a small bowl, combine the flour, granulated sugar, brown sugar, and cinnamon. Cut in the cold butter using a pastry cutter or fork until the mixture resembles coarse crumbs. Set aside.
Prepare the loaf batter: In a medium bowl, whisk together the flour, baking powder, baking soda, salt, cinnamon, and nutmeg.
In a large bowl, beat the softened butter, granulated sugar, and brown sugar until light and fluffy, about 2-3 minutes. Add the eggs one at a time, beating well after each addition. Stir in the vanilla extract.
Gradually add the flour mixture to the butter mixture, alternating with the sour cream or Greek yogurt, beginning and ending with the flour mixture. Mix until just combined.
Fold in the diced apples until evenly distributed throughout the batter.
Put the loaf together: Half of the batter should be added to the loaf pan. Over the batter, distribute half of the streusel topping. Continue with the leftover batter and topping of streusel.
Have fun.