Preheat the Oven: Preheat the oven to 350°F (175°C). Grease and lightly flour a Bundt pan or a 9×13-inch baking dish to ensure easy release.
Cream the Butter and Sugar: In a large mixing bowl, combine softened butter and granulated sugar. Beat until the mixture is light, fluffy, and pale in color, creating a smooth base for the cake.
Incorporate the Eggs and Vanilla: Add the eggs one at a time, blending well after each addition. Stir in the vanilla extract to enhance the flavor and aroma of the batter.
Add the Sweet Potatoes: Mix in the mashed sweet potatoes until the batter achieves a uniform texture and rich orange hue. This will contribute both moisture and flavor to the finished cake.
Combine Dry Ingredients: In a separate bowl, whisk together the all-purpose flour, baking powder, baking soda, salt, cinnamon, and nutmeg. Ensure even distribution of leavening agents and spices.
Alternate Dry and Wet Ingredients: Gradually add the dry ingredients to the creamed mixture, alternating with the milk or buttermilk. Begin and end with the dry ingredients. Mix gently until just combined to maintain a tender crumb.
Prepare for Baking: Transfer the batter into the prepared pan, smoothing the top with a spatula for an even rise.
Bake the Cake: Place in the preheated oven and bake for approximately 50 to 60 minutes, or until a toothpick inserted into the center comes out clean.
Prepare the Butter Glaze: While the cake bakes, melt butter in a small saucepan. Add granulated sugar and water, stirring constantly. Bring the mixture to a gentle boil and simmer for 2 to 3 minutes. Remove from heat and stir in vanilla extract for added depth.
Glaze the Cake: While the cake is still warm, use a skewer or toothpick to create small holes across the surface. Slowly pour the warm butter glaze over the cake, allowing it to absorb evenly into the crumb.
Cool and Serve: Allow the cake to cool in the pan before inverting onto a serving plate or slicing directly from the baking dish. Serve plain, with whipped cream, or a dusting of powdered sugar for an elegant presentation.