Preheat the oven to 350°F (175°C) and grease a 9-inch springform pan.
Whisk flour, baking powder, baking soda, and salt in a medium bowl.
Cream butter and sugar in another bowl until fluffy. Add eggs, vanilla, and buttermilk, mixing until smooth.
Gradually mix dry ingredients into the wet mixture to create the batter.
For the filling, beat cream cheese, sugar, egg, and vanilla until smooth and creamy.
For the streusel, mix flour, brown sugar, cinnamon, and cold butter until crumbly.
Spread half the batter into the pan, then layer the cream cheese filling evenly.
Top with the remaining batter and sprinkle the streusel topping generously.
Bake for 45 minutes or until the center sets. Cool before slicing.