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.
Assemble the loaf: Pour half of the batter into the prepared loaf pan. Sprinkle half of the streusel topping over the batter. Repeat with the remaining batter and streusel topping.
Enjoy.
