Preheat your oven to 350°F and grease a 9×5-inch loaf pan. Line it with parchment paper for easy removal.

In a small bowl, combine ¾ cup brown sugar and 1tsp cinnamon for the cinnamon swirl. Set aside.

In a medium bowl, mix ⅓ cup flour, ¼ cup brown sugar, and 1 tsp cinnamon for the crumb topping. Grate ¼ cup cold butter into the mixture, and use your hands to combine until it resembles coarse crumbs. Set aside.

In a separate bowl, whisk together 1.5 cups flour, 1tsp baking powder, ½tsp baking soda, salt, and cinnamon.

In a large bowl, cream together ½ cup (a stick) of softened butter and ¾ cup white sugar until light and fluffy. Beat in the eggs, one at a time. Add ½ cup Greek yogurt and vanilla, mixing until smooth.

Gradually add the dry ingredients to the wet ingredients, stirring until just combined. Be careful not to overmix. Fold in the diced apples. (Dice these small! About the size of mini dice.)

Pour half of the batter into the prepared pan. Sprinkle the cinnamon swirl mixture evenly over the top.

Add the remaining batter and top it with the crumb mixture.

Bake for 50-60 minutes or until a toothpick inserted into the center comes out clean. If the loaf browns too quickly, cover it loosely with aluminum foil. Let the loaf cool in the pan for 10-15 minutes before transferring it to a wire rack.