For the Cake

1 1/2 cups all purpose flour
1 teaspoon baking soda
1/2 teaspoon salt
1/4 cup very soft butter
1 cup granulated sugar
1 large egg
1 teaspoon vanilla extract
1 cup buttermilk

For the Raspberry Buttercream

12 fresh or frozen raspberries (thawed if frozen)

1/2 cup (1 stick) unsalted butter, softened
1 lb box powdered sugar
1/2 teaspoon raspberry extract (or vanilla)
2-3 tablespoons milk (as needed)

Preheat oven to 350 degrees F.  Lightly spray an 8 inch cake pan with baking spray and line with parchment paper.  Set aside.

For the Cake

In a medium bowl, add the flour, baking soda, and salt.  Stir to combine.  Set aside.

In a large mixing bowl, beat together the butter and sugar until light and creamy.  Add the egg and vanilla and beat to combine.   Add the flour mixture alternately with the buttermilk.  Begin and end with dry ingredients.

Pour the batter into the prepared pan.  Bake the cake for 30-35 minutes until light golden brown or until a toothpick inserted in the middle comes out  clean.  Cool in the pan for 10 minutes, then turn out onto a cooling rack to cool completely before frosting.

For the Raspberry Buttercream Frosting

Place the raspberries on a small plate and mash well with a fork and then press through a fine mesh strainer to remove the seeds.  Set aside.

In a large bowl with electric mixer at low speed,  beat butter on medium-high speed until pale and fluffy, about 2 minutes.  Add the powdered sugar, 1/2 cup at a time, beating well after each addition and scraping down sides of bowl as needed.  Beat in the raspberry puree and raspberry extract.  Add milk, if needed.  Beat at medium speed 1 to 2 minutes until creamy and is of desired consistency for frosting the cake.

Spread the buttercream over the top of the cake and around the sides of the cake.  Decorate as desired.