Pre-heat oven to 400 degrees Fahrenheit. Then, mix granulated sugar, cocoa powder and cinnamon in a small bowl to create your cinnamon sugar layer and set aside.
In a large mixing bowl, mix cream cheese, brown sugar and white sugar until well combined using a stand mixer or hand mixer.
Add applesauce to the creamed sugar and cream cheese. Beat until well combined. Then, add in eggs, one at a time, as well as the vanilla. Beat until well combined.
While mixing/beating on low speed, alternate adding-in buttermilk and dry ingredients.
In a 9 x 13 baking dish, spray with non-stick spray. Then, add in ½ the batter, top it with your cinnamon sugar mixture. Make sure the cinnamon sugar is evenly distributed on top of the batter. Next, use a toothpick, wooden skewer or knife to gently swirl the cinnamon sugar into the batter.
Top with the remaining ½ of the batter and spread evenly. Place into the oven and bake for 20 minutes.
While the coffee cake is baking, prepare the streusel by mixing the dry streusel ingredients in a bowl, then adding melted butter to it and mixing with a spatula or by hand to create streusel pieces. I think forming streusel by hand ensures nicely formed streusel pieces.
Once the cake has baked for 20 minutes, take it out of the oven. Drop the temperature to 325 degrees Fahrenheit. Then, carefully place the streusel on the cake until the whole pan is covered.
Bake the cake for an additional 30-40 minutes until a wooden skewer comes out clean from the center of the cake.
Cool to room temperature. Prepare the vanilla glaze by mixing together powdered sugar and milk/cream in a small bow. Drizzle the vanilla glaze on top. Serve and enjoy.