Preheat oven to 350 degrees. Line cupcake pan with cupcake liners.
In base of a stand mixer fit with paddle attachment, beat butter and sugar until lightened and fluffy, about 2 minutes. Next, beat in egg until combined, scraping down sides as needed.
Beat in crushed peach, vanilla extract, lemon juice, and lemon zest until well mixed, scraping down sides as needed.
In a small bowl, stir together flour, cornstarch, baking powder, and baking soda. Alternate beating flour mixture and milk into mixer, in about 3 additions each, scraping down sides as needed.
Finally, stir in fresh blueberries.
Fill cupcake liners about 2/3 full of batter. This recipe makes about 18 cupcakes.
Bake for 18-20 minutes, or until tops are light golden and a toothpick inserted into the center of one of the middle cupcakes comes out with just a few crumbs.
Let cupcakes cool completely before frosting.