Preheat oven to 325F, and prepare a 9x5 loaf pan with parchment paper, then set aside.
Make the cinnamon sugar mixture in a small bowl, then set aside.
In a large mixing bowl, whisk flour, baking powder, ground cinnamon, salt and ground nutmeg. Put this aside while you mix up your wet ingredients.
In a medium bowl, whisk together brown sugar, white sugar, Greek yogurt, oil, eggs and vanilla extract. Once well incorporated, transfer to the large bowl, mixing until no dry streaks.
Fold in the apples, then transfer about half of the batter in your prepared 9x5 pan.
Evenly sprinkle ½ to ¾ of the cinnamon sugar, followed by the rest of the batter. I like to use the back of a spoon or an offset spatula to even out the batter as best as I can, then take a knife and give it a swirl.
Top with the remaining cinnamon sugar, and bake for about 60 minutes, or until a toothpick comes out clean (aim for 202F if using an instant thermometer).
Set on a wire rack and allow it to cool for about 20 minutes then make your glaze by whisk ingredients into a small bowl.
Drizzle over as desired, and slice.