Preheat Oven & Prepare Pan: Preheat the oven to 350°F (177°C). Line a 12-cup muffin pan with cupcake liners.
Mix Dry Ingredients: In a large bowl, whisk together flour, baking powder, and salt. Set aside.
Cream Butter & Sugar: Beat butter, sugar, and lemon zest on medium-high speed until light and fluffy, about 3 minutes.
Add Eggs & Vanilla: Add eggs one at a time, followed by vanilla extract. Beat until combined.
Combine Wet & Dry Ingredients: Slowly alternate adding the dry ingredients and milk/lemon juice. Mix until just combined. Gently fold in the flour-coated blueberries.
Fill Cupcake Liners: Fill each liner about 2/3 full with batter. Bake for 18–21 minutes or until a toothpick inserted comes out clean. Let the cupcakes cool completely.
Make Frosting: Beat cream cheese and butter until smooth. Gradually add powdered sugar, vanilla, and salt, then beat until fluffy.
Frost the Cupcakes: Pipe or spread the frosting onto the cooled cupcakes. Garnish with lemon slices or extra blueberries if desired.