Make the bread

• Heat the oven to 350ºF. Coat a 9x5-inch loaf pan with cooking spray. Line the bottom and two long sides of the pan with a parchment paper sling, making sure it hangs over the sides by a few inches. Whisk 2 tablespoons of the granulated sugar and 1 teaspoon of the ground cinnamon together in a small bowl; reserve for topping.
• Melt 4 tablespoons unsalted butter in a large skillet over medium heat. Transfer to a large heatproof bowl.
• Add 1 ½ pounds peeled and diced apples, ¼ cup packed brown sugar, 1 teaspoon of the ground cinnamon, and 1 pinch kosher salt to the now-empty skillet (do not wipe out). Cook over medium heat, stirring occasionally, until the apples start to soften and the sugar is dissolved and syrupy, about 5 minutes. Turn off the heat.
• Whisk 1 ½ cups all-purpose flour, 1 ½ teaspoons baking powder, the remaining 1 teaspoon ground cinnamon, and ¼ teaspoon baking soda together in a medium bowl. Whisk in the remaining ¾ cup granulated sugar, ¼ cup neutral oil, 1 teaspoon vanilla extract, and ½ teaspoon kosher salt into the melted butter until combined.
• Whisk in 3 room temperature large eggs one at a time, whisking well after each addition. Whisk in ⅓ cup room temperature sour cream until combined and no streaks of sour cream remain. Fold in the flour mixture until just combined.
• Transfer half of the batter into the loaf pan (about 1 ½ cups) and spread into an even layer, going all the way to the edges. Top with half of the apple mixture (about 2 cups) and press it lightly into the batter. Dollop the remaining batter over the apples and spread to the edges, covering the apples completely. Scatter the remaining apple mixture evenly over the top. Sprinkle the cinnamon sugar evenly over the top.