Preheat the oven to 350°F (175°C). Grease and flour a 9-inch round cake pan.
In a large bowl, beat together 1 cup of sugar and the butter until light and fluffy. Beat in the egg and vanilla extract.
In another bowl, whisk together flour, baking powder, baking soda, and salt. Gradually add the dry ingredients to the butter mixture alternately with buttermilk, starting and ending with dry ingredients.
Pour half of the batter into the prepared cake pan. Mix the remaining sugar (1/4 cup) with 1 teaspoon of cinnamon, and brown sugar. Sprinkle evenly over the batter in the pan.
Carefully spread the remaining batter over the sugar mixture, and sprinkle the top with the remaining cinnamon.
Bake in the preheated oven for about 45 minutes, or until a toothpick inserted into the center comes out clean. Allow the cake to cool for 10 minutes in the pan before transferring to a wire rack to cool completely.