Preheat the Oven: Set your oven temperature to 350°F (175°C). Prepare a standard 12-cup muffin tin by lining it with paper liners or greasing it thoroughly with cooking spray.
Mix Dry Ingredients: In a large mixing bowl, add the all-purpose flour, granulated sugar, baking powder, baking soda, ground cinnamon, ground nutmeg, and salt. Whisk these ingredients together until they are well blended, ensuring there are no lumps.
Combine Wet Ingredients: In a separate bowl, whisk together the eggnog, vegetable oil, eggs, and vanilla extract until the mixture is smooth and uniform.
Combine Wet and Dry Mixtures: Gently pour the wet mixture into the dry mixture. Using a spatula or wooden spoon, stir until just combined—be careful not to overmix; it’s okay if the batter has a few lumps. If you’re including pecans, fold them gently into the batter at this point.
Prepare Topping Mixture: In a small bowl, combine the melted butter, brown sugar, and ground cinnamon. Use a fork to mix until the mixture achieves a crumbly texture.
Fill Muffin Cups: Evenly distribute the batter into the prepared muffin tin, filling each cup about two-thirds full. Generously sprinkle a portion of the topping mixture over each muffin.
Bake the Muffins: Place the muffin tin in the preheated oven and bake for 18-20 minutes. They are done when a toothpick inserted into the center of a muffin comes out clean.
Cool the Muffins: Once baked, let the muffins cool in the pan for approximately 5 minutes before carefully transferring them to a wire rack to cool completely.
Notes
For a festive touch, serve warm with powdered sugar and cinnamon.