Preheat oven to 350°F. Prepare muffin tin with 12 cupcake liners. Set aside.
In the bowl of a stand mixer fitted with paddle attachment, combine flour, sugar, baking powder, and salt. Add butter cubes. Mix on low speed until mixture resembles sand or almond flour.
Add eggs one a time, making sure first egg is incorporated before adding second egg. Mix on medium speed until well combined. Scrape down sides of bowl as needed.
Combine milk, vanilla, and sour cream in small container. With the mixer running on low speed, slowly add wet ingredients in a slow stream. Increase to medium speed and mix until batter is smooth. Scrape down sides of bowl as needed to ensure thorough mixing.
Divide batter evenly between prepared muffin tin, filling each cavity about ⅔ full. Bake for 16-18 minutes until toothpick inserted in center of cake comes out clean, or until cake lightly springs back when touched. Rotate pan halfway through baking. Let cupcakes cool in tin for 5 minutes before transferring to cooling racks.