Preheat your oven to 350°F (175°C). Line a muffin tin with paper liners or grease the cups.
In a medium-sized bowl, whisk together the flour, baking powder, baking soda, salt, cinnamon, and nutmeg. Set aside.
In a large mixing bowl, cream together the softened butter and 1 cup of granulated sugar until light and fluffy, about 2-3 minutes.
Add the eggs, one at a time, mixing well after each addition. Stir in the vanilla extract.
Alternate adding the dry ingredients** and the Greek yogurt to the wet ingredients, beginning and ending with the dry mixture. Mix until just combined. Be careful not to overmix; a few lumps are okay.
Spoon the muffin batter into the prepared muffin cups, filling each about 2/3 full.
Bake in the preheated oven for 18-20 minutes or until a toothpick inserted into the center of a muffin comes out clean.
While the muffins are baking, prepare the **cinnamon sugar topping**. In a small bowl, combine ¼ cup of granulated sugar and 2 tsp of ground cinnamon.
As soon as the muffins are done baking and still warm, **brush the tops** with melted butter and dip them into the cinnamon sugar mixture to coat evenly.
Allow the muffins to cool in the tin for about 5 minutes, then transfer them to a wire rack to cool completely.
