1/2 tsp salt
1 cup unsalted butter, softened
For the Cake:
2 1/2 cups all purpose flour
1 tsp baking powder
1/2 tsp baking soda
2 tsp cinnamon
1/2 tsp salt
¾ cup unsalted butter, very soft
Combine flour, baking powder, baking soda, cinnamon and salt in a medium bowl and whisk until well combined.In a large bowl, cream the butter and sugar together on medium-high speed until smooth and fluffy, about 3 minutes. Beat eggs in one by one, followed by vanilla extract. Alternately add the buttermilk and the flour mixture, making sure to end with an addition of dry ingredients. Don’t forget to scrape down the sides of the bowl with a spatula as you mix.
Scrape half of your batter into the greased, 10-inch tube pan that you prepared earlier. Smooth batter with a spatula and top with streusel. Scrape remaining batter into pan, on top of streusel, gently spreading it to the sides of the pan with your spatula.
Bake at 350F for 60-70 minutes, until a tester comes out clean.
Place cake on a wire rack and allow to cool for 15 minutes. Run a sharp knife around the around the outer and inner edges of the pan. Remove tube portion with cake attached. Run knife over the bottom, loosening the cake. Gently replace cake in the pan, which will support it as you turn it upside down. Place a clean dishtowel on top of the pan and a baking sheet on top of that.
Carefully flip pan over, turning cake out onto the baking sheet. Reinvert onto wire rack. Allow to cool completely.