• Preheat the oven to 350°F and grease an 8x8” square cake pan with baking spray and line with parchment paper so it overhangs the pan.

Make the Cinnamon Sugar Mixture

• In a small bowl, mix together the brown sugar and cinnamon. Set aside for later.

Make the Cake Batter

• In a large bowl, whisk together the sugar and eggs for 1 minute until pale and fluffy. Next, whisk in the milk, sour cream, melted butter, vanilla extract and salt, just until combined.
• Add the flour, baking powder, baking soda and cream of tartar, and whisk until no lumps remain and a batter forms. Don’t overmix otherwise the batter will become dense rather than fluffy.

Assemble the Cake

• Pour half the batter into the pan and spread into an even layer. Sprinkle the cake batter with half of the cinnamon-sugar mixture. Pour the remaining batter on top and spread into an even layer. Sprinkle with remaining cinnamon-sugar mixture, and use a butter knife to swirl everything around.
• Bake the cake in the center rack of the oven for 32-35 minutes, or until a toothpick inserted into the center comes out clean.
• Allow the cake to cool on a wire rack, in the pan, for 20 minutes. Then, carefully use the parchment paper overhang to lift the cake out of the pan and set back to fully cool before icing the cake.

Make the Cream Cheese Drizzle

• In a medium bowl, use a rubber spatula to press the confectioner's sugar into the cream cheese for 3 minutes, until the cream cheese has loosened and becomes smoother.
• Mix in the vanilla extract.
• Switch to a whisk and add 1 tablespoon of milk at a time, until the mixture is a smooth consistency.
• Drizzle over the mostly cooled cake.