Make the brown sugar cinnamon filling by whisking together the brown sugar, flour and cinnamon.
Whisk together the flour, brown sugar and cinnamon. Cut the cold and cubed butter into the mixture until it is completed incorporated.
Beat together the butter and oil until completely combined. Add the granulated sugar and beat. Add the eggs and vanilla extract and beat.
Add half of the dry ingredients and mix. Add half of the milk and mix. Repeat this process with the other halves of the dry ingredients and the milk.
Pour half of the batter into the pan and spread into an even layer. Sprinkle the filling mixture on top. Pour the other half of the batter on top. Top with the streusel.
Bake at 350 degrees Fahrenheit for 35-45 minutes until a toothpick inserted into the center comes out clean. Top with powdered sugar. Enjoy!