Preheat the Oven: Start by preheating your oven to 350°F (175°C). Grease a 9-inch round cake pan or line it with parchment paper for easy removal.

Mix the Dry Ingredients: In a medium bowl, whisk together the all-purpose flour, baking powder, baking soda, salt, and ground cinnamon. Set aside.

Cream the Butter and Sugar: In a large mixing bowl, beat the softened butter and granulated sugar using an electric mixer until light and fluffy, about 3-4 minutes.

Add the Eggs and Milk: Add the eggs, milk, and vanilla extract to the butter mixture and continue mixing until well combined.

Combine Wet and Dry: Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Be careful not to overmix, as this can make the cake dense.

Prepare the Streusel Topping: In a small bowl, combine the brown sugar, 1/2 teaspoon of cinnamon, and chopped nuts (if using). Use a fork to mix it together until the mixture resembles coarse crumbs.

Assemble the Cake: Pour half of the batter into the prepared cake pan. Sprinkle half of the streusel topping evenly over the batter. Pour in the remaining batter, followed by the rest of the streusel on top.

Bake the Cake: Bake in the preheated oven for 30-35 minutes, or until a toothpick inserted in the center comes out clean.

Cool and Serve: Allow the cake to cool in the pan for 10 minutes before transferring it to a wire rack to cool completely. Once cooled, slice and serve!