Preheat your oven to 325°F. Grease a 9-inch springform pan with butter and line the bottom with parchment paper.

In a large mixing bowl, cream together the butter and cream cheese until smooth and creamy.

Add the sugar to the bowl and beat for an additional 2-3 minutes, or until the mixture becomes light and fluffy.

Add the eggs one at a time, beating well after each addition.

Add the vanilla extract and mix until combined.

Sift the flour into the bowl and mix until just combined. Be careful not to overmix, as this can make the cake tough.

Pour the batter into the prepared pan and smooth out the top with a spatula.

Drizzle the sweetened condensed milk over the top of the cake, making sure to cover the entire surface.

Bake the cake in the preheated oven for 55-60 minutes, or until a toothpick inserted in the center comes out clean.

Allow the cake to cool in the pan for 15-20 minutes, then remove it from the pan and transfer it to a wire rack to cool completely.

Slice and serve the cake warm or at room temperature, with a scoop of vanilla ice cream on top if desired.