Preheat the oven to 350°F (175°C) and grease a 9-inch round cake pan.
In a bowl, whisk flour, baking powder, baking soda, salt, and espresso powder.
In another bowl, beat butter and sugar until creamy. Add eggs and vanilla, mixing until smooth.
Stir in sour cream. Gradually add dry ingredients, mixing until fully combined.
Pour batter into prepared pan.
For the streusel, mix brown sugar, flour, butter, and cinnamon. Sprinkle over the batter.
Bake for 30-35 minutes or until a toothpick inserted comes out clean.
Let the cake cool on a rack before serving.