Preheat your oven to 375°F (190°C). Line a standard muffin pan with 8 paper liners to prevent sticking and ensure even baking.

In a small bowl, whisk together the all-purpose flour, ground cinnamon, baking powder, baking soda, and salt until well combined. This ensures the leavening agents and spices are evenly dispersed throughout the batter.

In a large bowl, whisk the eggs, granulated sugar, and light brown sugar together vigorously for about 90 seconds until slightly pale and combined. Add the melted (but not hot) unsalted butter and vanilla extract, then whisk for an additional 30 seconds. I like to use packed light brown sugar if baking with tart apples like Granny Smith—it helps balance their tanginess.

Using a wooden spoon, gently stir the dry ingredient mixture (from Step 2) into the wet ingredients (from Step 3) just until combined—the batter will be thick. Fold in the grated apples and walnuts (if using); the moisture from the apples will help loosen the batter. Remove any large pieces of apple peel after grating for a smoother texture. Don’t overmix to keep the muffins tender.

In a small bowl, stir together the granulated sugar and ground cinnamon for the topping. Divide the batter evenly among the lined muffin cups and sprinkle the cinnamon-sugar mixture generously over each muffin so they develop a beautiful crust as they bake. I always use up all the topping for maximum flavor on every bite.

Bake in the preheated oven for 23 to 25 minutes, or until the muffin tops are a deep golden color and a toothpick inserted into the center comes out clean.

Place the muffin pan on a wire rack to cool. Serve the muffins warm for the best flavor and texture. I like to serve them slightly warm with a bit of butter for an extra treat.