Preheat and prep: Preheat your oven to 350°F (175°C).
Line a 12-cup muffin tin with paper liners. This helps the cupcakes release cleanly and bake evenly.
Whisk the dry ingredients: In a medium bowl, whisk flour, baking powder, baking soda, and salt. Set aside.
This keeps the leaveners evenly distributed.
Cream butter and sugar: In a large bowl, beat the softened butter and sugar together on medium speed for 2–3 minutes until light and fluffy. You’re adding air here, which helps create a tender crumb.
Add eggs and vanilla: Beat in the eggs one at a time, scraping down the bowl as needed. Mix in the vanilla extract (and paste, if using) until smooth.
Combine wet and dry in parts: On low speed, add half the dry ingredients.
Mix just until incorporated. Add the milk and sour cream, then the remaining dry ingredients. Stop mixing as soon as no dry streaks remain.
Overmixing makes cupcakes tough.
Portion the batter: Divide the batter evenly among the liners, filling each about 2/3 to 3/4 full. Using a scoop helps keep sizes consistent.
Bake: Bake for 16–20 minutes, or until the tops spring back when lightly touched and a toothpick comes out clean or with a few moist crumbs. Avoid opening the oven early; wait until at least 15 minutes have passed.
Cool: Let the cupcakes rest in the pan for 5 minutes, then transfer to a wire rack to cool completely.
Frost only when cool to prevent melting.
Frost and finish: Top with your favorite frosting and a few sprinkles, if you like. A simple vanilla buttercream or lightly sweetened whipped cream both work well.