Preheat your oven to 400 degrees and line a 12-cup muffin tin with paper cups. In a small bowl, whisk together your dry ingredients until well combined.
In a large bowl, using a mixer, cream together butter and sugar. Add in the egg and vanilla, and beat until smooth. Add half of the flour mixture, stir, pour in buttermilk, stir, and then add the remaining flour. Stir until well combined.
Distribute evenly in muffin cups, filling about 2/3 full. Bake for 18-20 minutes. Allow to cool completely before frosting.
Store in the refrigerator for up to five days.
Cream Cheese Frosting:
Allow cake/cupcakes to cool completely before frosting.
Beat cream cheese with butter and vanilla until combined. Gradually add powdered sugar. Continue to add more powdered sugar until you reach a consistency and sweetness that fits your taste.
Recommended: Fit a large pastry bag (around 16 inches) with a Wilton 1M tip and add frosting to fill the bag about halfway full. Start the swirl from the center. As you near the outside, release pressure and press the tip against the swirl to make it look "seamless."