1 1/2 cups AP flour
1 cup sugar
1 1/2 tsp baking powder
1/2 tsp table salt (1 tsp kosher)
8 Tbsp unsalted butter (room temperature)
1/2 cup sour cream
1 large egg (room temperature)
2 large egg yolks (room temperature)
1 1/2 tsp vanilla extract
Adjust oven rack to middle position; heat oven to 350 degrees. Line standard muffin/cupcake tin with paper or foil liners.
Whisk together flour, sugar, baking powder, and salt in bowl of standing mixer fitted with paddle attachment. Add butter, sour cream, egg and egg yolks, and vanilla; beat at medium speed until smooth and satiny, about 30 seconds. Scrape down sides of bowl with rubber spatula and mix by hand until smooth and no flour pockets remain.
Divide batter evenly among cups of prepared tin using 2-ounce ice cream scoop or heaping tablespoon. Bake until cupcake tops are pale gold and toothpick or skewer inserted into center comes out clean, 20 to 24 minutes. Use skewer or paring knife to lift cupcakes from tin and transfer to wire rack; cool cupcakes to room temperature, about 45 minutes.