Preheat oven to 350 degrees F. Grease and line a 9 inch cake pan with parchement paper.
In the bowl of a stand mixer beat the butter and sugar until light and fluffy. Add in eggs 1 at a time and beat after each addition. Add the lemon zest and lemon juice. Then add in the yogurt.
Mix together the flour, baking soda and salt in a separate bowl.
Alternate adding in the dry ingredients and the milk into the batter mixture. Mix until combined.
Pour batter into prepared pan and bake for 35-40 minutes or until a toothpick inserted comes out clean.
Let cool for 15 minutes before flipping onto a cooling rack
for the raspberry puree
In a small saucepan, mix together all ingredients. Bring mixture to a boil. Cook until the raspberries break down and you are left with a smooth puree.
Stir occasionally so it does not burn
Strain the mixture through a sieve or cheese cloth to get out the seeds. Let the mixture cool.
For the buttercream
Beat the butter until smooth and fluffy. Slowly add in the powdered sugar. Add in the milk and continue to mix. Beat until fluffy. Add in the raspberry puree. Save the puree remains to garnish the top of the cake.
Assembly
Once the cake is cooled, frost the top of the cake with the raspberry buttercream. If desired, use the remaining puree and drizzle on top of the cake. Garnish with fruit if desired.