Preheat the oven to 350 F (177 C). Grease and line the bottom of a 9 inch (23 cm) springform or cake pan with parchment paper.
In a large bowl, whisk together the flour, brown sugar, granulated sugar and ground cinnamon for the crumble topping. Work in the melted and cooled butter a couple of teaspoons at a time until a sand like texture develops. Place the bowl in the fridge until the apple crumb coffee cake is ready for topping. 1 cup (120 g) all purpose flour, 5 tablespoons (67 g) light brown sugar, 3 tablespoons (38 g) granulated sugar, 6 tablespoons (85 g) unsalted butter, melted
In a small bowl toss the peeled, diced apples into ¼ teaspoon ground cinnamon and set aside.
2 cups peeled and diced cinnamon apples
In a medium bowl whisk the all purpose flour, ground cinnamon, baking powder, baking soda and salt together until well combined.
2 cups (240 g) all purpose flour, 1 teaspoon ground cinnamon , 2 teaspoons baking powder, ¼ teaspoon baking soda, ½ teaspoon salt
In a large mixing bowl, cream the sugar and butter together until light and fluffy. This takes about 2-3 minutes on medium speed. On low, beat in the eggs and vanilla extract until smooth and well combined. ½ cup (113 g) unsalted butter, room temperature, 1 cup (200 g) granulated sugar, 2 large eggs (US), room temperature, 1 teaspoon (5 ml) vanilla extract
Alternating dry ingredients and sour cream, mix in ⅓ of the dry ingredients into the wet, followed by ½ of the sour cream. Repeat until all the ingredients are just combined. Fold in the the cinnamon apples until just combined. 1 cup (240 g) sour cream, room temperature
Evenly spread the cinnamon apple coffee cake batter into the prepared pan. Top with the cinnamon crumb, making sure to break any extra large pieces.
Bake the coffee apple cake for 50 - 55 minutes or until a toothpick inserted into the center of the cinnamon apple crumb cake comes out with a few moist crumbs.
Cool the pan in the pan for 15 - 20 minutes. Gently remove the cake from the pan and transfer to a serving plate. Top with powdered sugar or a glaze, slice and enjoy!