Preheat your oven to 350°F (175°C) and line a cupcake pan with liners.
In a mixing bowl, cream together the softened butter and sugar until light and fluffy. Add in the egg, vanilla extract, and strawberry puree, mixing until well combined.
In another bowl, whisk together the flour, baking powder, and salt. Gradually add the dry ingredients to the wet mixture, alternating with the milk.
Fill the cupcake liners with the batter and bake for 15 minutes or until a toothpick comes out clean.
Let the cupcakes cool completely before frosting with the strawberry buttercream.
For the buttercream, beat the softened butter until creamy, then gradually add powdered sugar, strawberry puree, vanilla extract, and salt until smooth.
Notes
These cupcakes are best enjoyed fresh. You can store them in an airtight container for up to three days.