Preheat your oven to 350°F (175°C). Butter and lightly flour 6 to 8 ramekins (depending on size) to prevent sticking. Set them on a baking sheet to make handling easier.

In a large bowl, cream the softened butter and sugar together using an electric mixer or whisk until the mixture is light and fluffy. Add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract.

In a separate bowl, whisk together the all-purpose flour, baking powder, and salt. Gradually add the dry ingredients to the butter mixture, alternating with the milk or buttermilk. Start and end with the dry ingredients. Mix until just combined; do not overmix.

In a medium bowl, beat the softened cream cheese until smooth. Add the sugar, egg, and vanilla extract, mixing until creamy and well combined.

Divide the cake batter evenly among the prepared ramekins, filling each about two-thirds full. Spoon a layer of the cream cheese topping on top of each ramekin, spreading gently to cover the batter.

Place the baking sheet with ramekins into the oven and bake for 45-50 minutes or until a toothpick inserted into the cake (not the topping) comes out clean. Remove from oven and allow to cool in the ramekins for 10-15 minutes before serving.