Preheat the oven to 350°F (175°C). Grease and flour two 9-inch round cake pans.
In a large mixing bowl, cream together the softened butter and granulated sugar until light and fluffy.
Add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract and lemon zest.
In another bowl, whisk together the flour, baking powder, and salt.
Gradually add the dry ingredients to the butter mixture, alternating with the milk. Mix until just combined.
Gently fold in the fresh raspberries.
Divide the batter evenly between the prepared cake pans.
Bake for 25-30 minutes, or until a toothpick inserted into the center comes out clean.
Allow the cakes to cool in the pans for 10 minutes before transferring to wire racks to cool completely.
While the cakes are cooling, prepare the frosting by beating the softened butter until creamy.
Gradually add the powdered sugar, mixing well.
Add the lemon juice and lemon zest, and beat until smooth. Adjust consistency with milk if needed.
Once the cakes are completely cooled, spread a layer of frosting on top of one cake layer, then place the second layer on top.
Frost the top and sides of the entire cake and decorate with additional raspberries if desired.