Make the Raspberry Puree

1. Place the raspberries, sugar, and lemon juice in a small saucepan.
2. Cook over low heat for 10 to 15 minutes, stirring often, until the raspberries break down and the mixture reduces slightly.
3. Blend the mixture with an immersion blender or regular blender until smooth.
4. Strain through a fine mesh sieve to remove the seeds, then let the raspberry puree cool completely.

Make the Lemon Cupcakes

1. Preheat the oven to 350°F (180°C) and line a cupcake pan with paper liners.
2. Mix the buttermilk with the lemon juice and set aside.
3. Cream the softened butter, sugar, and lemon zest for 2 to 3 minutes until light and fluffy.
4. Add the eggs and vanilla extract, then mix until smooth.
5. Stir in the cake flour, baking powder, and salt, alternating with the buttermilk mixture, until the batter is just combined.
6. Fill the cupcake liners about ⅔ full.
7. Bake for 18 to 20 minutes, or until a toothpick inserted in the center comes out clean.
8. Cool the cupcakes completely before frosting.

Make the Frosting

1. Place the cream cheese, heavy cream, powdered sugar, raspberry puree, and vanilla extract in a large bowl.
2. Whip with an electric mixer on low speed, then medium speed, until thick, fluffy, and stable.
3. Pipe the raspberry cream cheese frosting onto the cooled lemon cupcakes.
4. Decorate with a fresh raspberry on top.