Preheat the oven to 350°F (175°C). Grease and line a 9x13-inch sheet pan with parchment paper.
In a medium bowl, whisk together flour, baking powder, and salt. Set aside.
In a large bowl, beat together granulated sugar and softened butter until light and fluffy.
Add eggs, one at a time, mixing well after each addition. Stir in vanilla extract.
Gradually add the dry ingredients to the wet mixture, alternating with the milk, and mix until just combined.
Pour the batter into the prepared sheet pan and spread it evenly.
In another bowl, beat softened cream cheese until smooth, then add sour cream and powdered sugar, mixing until combined. Stir in vanilla extract.
Spread the cheesecake mixture evenly over the cake batter.
Bake for 35-40 minutes, or until the cheesecake layer is set and the cake is golden around the edges. Let it cool completely.
Once cooled, slice into squares and garnish with optional toppings like fruit, whipped cream, or chocolate drizzle.