A rich, moist cake with a swirl of cinnamon and a buttery crumb topping, perfect for breakfast or a sweet afternoon treat.

1 1/2 cups all-purpose flour

1 teaspoon baking powder

1/2 teaspoon baking soda

1/4 teaspoon salt

1/2 cup unsalted butter, softened

1 cup granulated sugar

2 large eggs

1 teaspoon vanilla extract

1 cup sour cream

1/2 cup packed light brown sugar

1 tablespoon ground cinnamon

1/2 cup chopped walnuts (optional)

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Preheat the oven to 350°F (175°C). Grease and flour a 9-inch round cake pan or an 8x8-inch square pan.
In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.
In a large bowl, cream together the softened butter and granulated sugar until light and fluffy, about 3-4 minutes.
Add the eggs, one at a time, beating well after each addition. Stir in the vanilla extract.
Gradually add the dry ingredients, alternating with the sour cream, beginning and ending with the dry ingredients. Mix until just combined.
In a small bowl, combine the brown sugar, cinnamon, and chopped walnuts (if using).
Pour half of the cake batter into the prepared pan. Sprinkle half of the cinnamon mixture over the batter. Repeat with the remaining batter and cinnamon mixture.
Using a knife or skewer, swirl the cinnamon mixture into the batter to create a marbled effect.
Bake for 35-40 minutes, or until a toothpick inserted into the center comes out clean.
Let the cake cool in the pan for 10 minutes before transferring to a wire rack to cool completely.

If you’re allergic to nuts or prefer a nut-free version, omit the walnuts.

For a gluten-free version, substitute the all-purpose flour with a gluten-free flour blend.

Add a pinch of nutmeg or allspice to the cinnamon mixture for extra flavor.

This cake can be made a day or two ahead, and it actually tastes better as the flavors meld.