Wash and hull the strawberries, then purée them in a blender or food processor until smooth. Strain the purée through a fine sieve to remove seeds, collecting about 1/4 cup of strawberry juice. Measure and set aside.
Preheat the oven to 350°F (175°C) and line a cupcake pan with paper liners. In a large mixing bowl, beat together the softened butter and sugar with an electric mixer until light and fluffy, about 2-3 minutes. The mixture should be pale and creamy.
Add eggs one at a time to the butter mixture, beating well after each addition. Mix in vanilla extract until combined. The batter should thicken and become smooth.
In a separate bowl, whisk together the sifted flour. In another small bowl, combine the strawberry juice with milk. Gradually add the dry ingredients to the wet mixture in three parts, alternating with the strawberry-milk mixture, starting and ending with flour. Fold gently until just combined; do not overmix.
Pour the strawberry purée into the batter and gently fold it in until the color is evenly distributed, resulting in a bright pink batter with streaks of fruit.
Spoon or scoop the batter into the prepared cupcake liners, filling each about two-thirds full. Bake in the preheated oven for 20 minutes, or until the tops are lightly golden and a toothpick inserted into the center comes out clean. The cupcakes should feel springy to the touch.
