Preheat the oven to 350°F and line two standard muffin pans with 24 cupcake liners.
In a medium bowl, whisk together 3 cups all-purpose flour, 1 tablespoon baking powder, and ½ teaspoon salt. Set aside.
In a large mixing bowl, beat 1 cup unsalted butter and 2 cups granulated sugar until light and fluffy, about 2 to 3 minutes.
Add 4 large eggs, one at a time, beating well after each addition and scraping down the sides of the bowl as needed.
Mix in 3 tablespoons lemon zest, 2 tablespoons fresh lemon juice, and 1 teaspoon vanilla extract until combined.
Alternate adding the flour mixture and 1 cup buttermilk to the butter mixture, beginning and ending with the flour mixture. Mix just until incorporated after each addition. Do not overmix.
Divide the batter evenly among the prepared cupcake liners, filling each about two-thirds full.
Bake for 15 to 20 minutes, or until a toothpick inserted into the center of a cupcake comes out clean.
Let the cupcakes cool in the pan for 5 minutes, then transfer them to a wire rack to cool completely before frosting.