Make the cupcakes: Heat oven to 350° F. Line a standard 12-cup muffin tin with paper liners. In a medium bowl, whisk together the flour, lemon zest, baking powder, and salt; set aside.
Using an electric mixer, beat the butter and sugar on medium-high until fluffy, 2 to 3 minutes. Beat in the eggs, one at a time, then the vanilla, scraping down the sides of the bowl as necessary.
Reduce mixer speed to low. Add the flour mixture in 3 additions and the milk in 2 additions, beginning and ending with the flour mixture. Mix just until combined (do not overmix).
Divide the batter evenly among the muffin cups. Bake until a toothpick inserted in the center comes out clean, 15 to 20 minutes. Cool in the tin for 10 minutes, then transfer to rack(s) to cool completely.
While the cupcakes are cooling, make the raspberry buttercream frosting. In a food processor or blender, puree the raspberries. Pour raspberries through a fine sieve into a bowl, pressing on solids, to eliminate the seeds. Place butter, half of the powdered sugar, and raspberry puree into mixing bowl. Beat over low speed until well-blended. Add the other half of the sugar, increase speed to medium. Mix until light and fluffy.