0.5cupunsalted butter, softened at room temperature
1largeegg
1teaspoonvanilla extract
1cupbuttermilk (or substitute by mixing 1 cup of milk with 1 tablespoon of vinegar)
0.5cupbrown sugar, packed tightly
1tablespoonground cinnamon (for the swirl mixture)
0.25cupchopped walnuts (optional, for added crunch)
Instructions
Begin by preheating your oven to 350°F (175°C). Prepare a muffin tin by lining it with paper liners or greasing the muffin cups with butter or cooking spray.
In a large mixing bowl, whisk together the all-purpose flour, granulated sugar, baking powder, baking soda, salt, and 1 teaspoon of ground cinnamon. Ensure all dry ingredients are combined well to avoid clumps.
In a separate medium bowl, cream the softened butter with the remaining granulated sugar using an electric mixer or a spatula until the mixture is light, fluffy, and pale in color. This should take about 2-3 minutes.
Add the egg and vanilla extract to the butter-sugar mixture. Beat until the mixture is smooth and well combined, ensuring no egg is left unincorporated.
Gradually add the dry ingredients to the butter mixture in three increments, alternating with the buttermilk. Start and end with the dry ingredients. Mix only until the batter is just combined; overmixing can lead to dense muffins, so be gentle!
In a small bowl, mix the packed brown sugar with 1 tablespoon of ground cinnamon until evenly distributed.
Fill each muffin cup about halfway with the batter. Then, sprinkle a generous layer of the cinnamon-brown sugar mixture over the batter in each cup. Fill the cups with more batter until they are about three-quarters full.
Using a toothpick or a small knife, gently swirl the top layer of batter with the cinnamon filling, creating a beautiful marbled effect. If you’re using walnuts, sprinkle them on top for added texture and flavor.
Place the muffin tin in the preheated oven and bake for 18-22 minutes. To check for doneness, insert a toothpick into the center of a muffin; it should come out clean when they are fully baked.
Once baked, let the muffins cool in the pan for about 5 minutes. Then, transfer them to a wire rack to cool completely. This allows airflow around the muffins and helps them retain their fluffy texture.
Notes
Serve warm, optionally dusted with powdered sugar or drizzled with a simple glaze.