Preheat & Prep: Preheat your oven to 350°F (175°C). Grease and flour a 9×13-inch baking pan or bundt pan.

Mix Wet Ingredients: In a large mixing bowl, cream together the butter and sugar until light and fluffy. Beat in the eggs one at a time. Stir in the sour cream and vanilla extract.

Combine Dry Ingredients: In a separate bowl, whisk together the flour, baking powder, baking soda, and salt. Gradually add the dry ingredients to the wet ingredients, mixing just until combined.

Make the Cinnamon-Sugar Swirl: In a small bowl, mix together the brown sugar, cinnamon, and nuts (if using).

Assemble the Cake: Spread half of the batter into the prepared pan. Sprinkle half of the cinnamon-sugar mixture over the batter. Add the remaining batter and top with the rest of the cinnamon-sugar mixture. Use a knife or skewer to swirl the layers slightly.

Bake: Bake for 35–40 minutes (for a 9×13-inch pan) or 50–55 minutes (for a bundt pan), or until a toothpick inserted into the center comes out clean.

Cool & Glaze (Optional): Let the cake cool in the pan for 10–15 minutes before transferring to a wire rack. If using the glaze, mix powdered sugar, milk, and vanilla in a small bowl, then drizzle over the cooled cake.