Preheat the oven to 350°F (177°C). Line a 12-cup muffin pan with cupcake liners. This recipes yields about 15 cupcakes, so you’ll have a 2nd batch.
Make the batter: Whisk the flour, baking powder, and salt together in a large bowl. Set aside.
Using a handheld or stand mixer fitted with a paddle attachment, beat the butter, sugar, and lemon zest together on medium-high speed in a large bowl until creamed, about 2 minutes. Scrape down the sides and bottom of the bowl as needed. Add eggs and vanilla extract, and then beat on medium-high speed until combined, about 1 minute. Scrape down the sides and bottom of the bowl as needed. Add the dry ingredients and then turn the mixer on low speed and slowly pour in the milk and lemon juice. Beat until just combined. Fold in the floured blueberries. Do not overmix.
Pour/spoon the batter into the liners—fill only 2/3 full to avoid spilling over the sides. Bake for 18–21 minutes, or until a toothpick inserted in the center comes out clean. For around 30–36 mini cupcakes, bake for about 11–13 minutes, same oven temperature. Allow the cupcakes to cool completely before frosting.
