Preheat your oven to 350°F (175°C). Grease a baking pan.
In a mixing bowl, combine flour, baking powder, and salt. In another bowl, cream together butter and sugar, then add eggs and vanilla. Mix in the milk and rhubarb. Combine with dry ingredients.
In a separate bowl, beat together cream cheese, sugar, egg, and vanilla.
In a third bowl, mix flour, brown sugar, cold butter, and cinnamon to form streusel.
Layer half of the cake batter in the baking pan, followed by the cream cheese mixture, then the remaining cake batter, and top with streusel.
Bake for 45 minutes or until a toothpick comes out clean.
Notes
Let the cake cool before serving. It pairs well with coffee.