1. Preheat oven to 350°F (177°C). Line a cupcake pan with paper liners.

2. In a medium bowl, whisk together the flour, baking powder, baking soda (if using), and salt. Set aside.

3. In a large bowl or using a stand mixer with a paddle attachment, beat the softened butter, vegetable oil (if using), sugar, and lemon zest on medium-high speed for about 2–3 minutes until creamy and light in color. Scrape down the sides as needed.

4. Add eggs one at a time along with vanilla extract, beating well after each addition.

5. Combine milk (or buttermilk), fresh lemon juice, and optional sour cream in a separate bowl.

6. Add dry ingredients to the butter mixture in three parts, alternating with the milk-lemon juice mixture, beginning and ending with the dry ingredients. Mix on low speed and stir just until combined. Avoid overmixing to keep cupcakes light and fluffy.

7. Gently fold in the floured blueberries using a rubber spatula to avoid breaking them.

8. Fill cupcake liners about two-thirds to three-quarters full to prevent overflow.

9. Bake for 18–21 minutes (or 11–13 minutes for mini cupcakes) or until a toothpick inserted in the center comes out clean.

10. Cool cupcakes in the pan for 5 minutes, then transfer to a wire rack to cool completely before frosting.

Frosting Instructions:

1. Beat the softened cream cheese and butter on medium speed until smooth (about 2 minutes).

2. Gradually add the confectioners’ sugar and lemon juice, beating on low until incorporated, then increase to medium-high and beat for 2 minutes until creamy and fluffy.

3. Mix in vanilla extract, pinch of salt, and optional lemon zest.

4. Refrigerate the frosting for at least 20 minutes before piping or spreading if you want firmer consistency.

5. Frost completely cooled cupcakes and garnish with lemon slices, extra blueberries, or additional lemon zest if desired.