Apple Cinnamon Coffee Cake with Cinnamon Streusel

Preheat oven to 350°F. Line an 8-inch baking pan with parchment paper, leaving overhang on all four sides. If using a round pan, lightly grease bottom and sides of pan with baking spray prior to lining the bottom of the pan with parchment paper. Set aside.
In a medium bowl, combine dry streusel ingredients. Mix in melted butter. Using a fork, gently toss ingredients until only small chunks remain. Transfer mixture to a clean rimmed baking pan. Set aside.
In a large bowl or stand mixer, cream together butter and sugars. Scrape bowl as needed. Mix in one egg at a time, followed by vanilla, baking powder, baking soda, salt and spices. Alternate additions of flour and sour cream. Mix until just combined and no streaks remain. Transfer batter to prepared baking pan. Spread out evenly using a small offset spatula. Set aside.
Peel and slice or chop apples. Toss with 1/2 teaspoon ground cinnamon. Add cinnamon apples to the top of your batter.Top off with prepared streusel.
Bake at 350°F for 45-50 minutes or until a toothpick inserted in the center of the cake comes out clean. Cool completely on a wire rack.
When cake is room temperature, carefully remote cake by pulling up and outwards on parchment paper. Transfer to a serving tray or platter.
In a small bowl, whisk together powdered sugar, milk and vanilla extract. Drizzle over cooled cake.
Slice and serve. Store remaining cake in an airtight container for up to several days.