Preheat your oven to 350°F (175°C). Grease and flour your 9x13 inch baking pan to prevent sticking.
In a small bowl, combine 1 cup of lightly packed brown sugar, 1 teaspoon of ground cinnamon, and 5 tablespoons of unsalted butter. Mix until crumbly and set aside.
In a mixing bowl, beat together 16 ounces of softened cream cheese, 1/2 cup of granulated sugar, 1 teaspoon of vanilla extract, and 1 large egg until smooth and creamy. Set aside.
In a separate bowl, whisk together 3 cups of all-purpose flour, 1 teaspoon of baking soda, 1 teaspoon of baking powder, and 1/2 teaspoon of sea salt.
In a large mixing bowl, cream together 1 cup of granulated sugar and 1 cup of softened unsalted butter until light and fluffy.
Add 1 large egg, 1 cup of sour cream, and 2 teaspoons of vanilla extract to the butter mixture. Mix until well combined.
Gradually add the dry ingredients to the wet mixture. Mix until just combined; do not overmix.
Spread half of the batter evenly into the prepared baking pan. Sprinkle half of the cinnamon filling over the batter, followed by the cream cheese filling. Top with the remaining batter and finish with the remaining cinnamon filling.
Bake in the preheated oven for 35-40 minutes, or until a toothpick inserted into the center comes out clean.
Allow the cake to cool in the pan for about 10 minutes, then transfer it to a cooling rack. Once cooled, whisk together the powdered sugar, melted butter, vanilla extract, and milk to create a glaze. Drizzle the glaze over the cake before slicing and serving.