Preheat a muffin or cupcake pan to 350°F and line it with cupcake liners.
Whisk together 1 1/4 cups flour, 1 1/4 teaspoons baking powder, and 1/2 teaspoons salt in a medium basin. Reserve flour mixture.
5 minutes at medium-high speed, scraping the basin as necessary, cream together the butter and sugar in an electric mixer. The mixture should be thick and airy.
Add eggs one at a time, beating well with each addition then scrape down the bowl. Add 2 tsp vanilla and beat to combine.
Mix the flour mixture in thirds while alternating with the buttermilk, ensuring that each addition is thoroughly incorporated. Reduce the mixer speed to medium. Beat, scraping the basin as necessary, until smooth and just combined; avoid overmixing. Evenly distribute the batter into a 12-count lined muffin or cupcake pan until it is two-thirds full.
At 350 degrees Fahrenheit, bake for 20 to 23 minutes, or until a toothpick inserted into the center comes out clear. Before frosting, transfer to a wire rack and allow to settle to room temperature after 5 minutes of cooling in the pan.