Preheat the oven to 350°F. Prepare a 9x5-inch loaf pan by spraying it with non-stick spray.
In a large bowl, cream together ½ cup salted butter and ⅔ cup granulated sugar until smooth.
Then, beat in the 2 large eggs, one at a time, mixing after each addition and scraping down the sides of the bowl.
Mix in 1 teaspoon vanilla extract.
Fold in 1½ cups all-purpose flour and 1 teaspoon baking powder. Mix only until blended - do not overmix.
Add ½ cup Greek yogurt and ¼ cup whole milk into the batter and gently mix just until smooth. Set this aside.
Peel and dice 2 medium apples. Add the diced apples to a bowl with ½ cup light brown sugar and 1 teaspoon ground cinnamon and stir to coat.
In a separate bowl, stir together ¼ cup light brown sugar, ½ Tablespoon ground cinnamon, and 1 teaspoon granulated sugar and set this aside.
Pour half of the batter into the prepared loaf pan. Then layer on half the apple mixture and sprinkle half of the brown sugar and cinnamon mixture on top of the apple layer. Gently swirl a knife through the layers.
Then repeat the layers one more time: batter, apple mixture, and end with the brown sugar and cinnamon mixture. Then, use a knife to swirl through the layers again.
Bake the loaf for 50 minutes or until a toothpick or cake tester inserted into the middle comes out with no batter sticking to it. If it's not done after 50 minutes, add 5 minutes and check again. If the loaf starts getting dark on top before the loaf is fully baked, tent the loaf with a piece of tin foil over the top to protect it from burning.
When the loaf is removed from the oven it needs to cool for at least 30 minutes before you add the glaze so that istdoesn't soak into the top.
While the loaf is cooling, prepare the glaze by whisking together 1 cup powdered sugar, 3 Tablespoon heavy cream, and 1 teaspoon vanilla extract until smooth. You can thicken it by using more powdered sugar, or thin it by using more cream.
1 cup powdered sugar, 3 Tablespoon heavy cream, 1 teaspoon vanilla extract