1-Preheat oven and prepare pan: Start by preheating your oven to 350°F (175°C) and greasing a 9-inch baking pan this helps the cake release easily after baking.

2-Mix dry ingredients: In a medium bowl, whisk together the dry ingredients like flour, baking powder, baking soda, salt, and cinnamon to distribute them evenly.

3-Combine wet ingredients: Then, in a large bowl, mix the wet ingredients including softened butter, sugar, eggs, vanilla, sour cream, and milk until they form a smooth batter.

4-Blend batter and add topping: Next, gently combine the wet and dry mixtures, stirring just until everything is incorporated to keep the cake light and fluffy. Pour the batter into your prepared pan and add the cinnamon crumb mixture on top for that irresistible streusel.

5-Bake and cool: Bake for 30-35 minutes, checking with a toothpick to ensure it’s done pull it out when the toothpick comes out clean. After baking, let the cake cool in the pan for about 10 minutes before transferring it to a wire rack. For the optional icing, whisk together the confectioners’ sugar, vanilla, and heavy cream or milk, then drizzle it over the cooled cake. This method works well with dietary swaps, so feel free to adjust as needed for a personalized touch.