Preheat oven to 325 degrees and grease a bundt pan with butter and flour. Defrost the raspberries.
Cream the butter and sugar until light and fluffy in a Kitchen Aid standing mixer, about 5 minutes.
Add the eggs one at a time, making sure to incorporate each one. Add the vanilla.
In a separate bowl, whisk together the flour, baking soda and salt.
Add the flour and sour cream alternately, 1/3 at a time, until combined.
In a bowl, mash the defrosted raspberries with a fork (you can use fresh, but frozen works better) until it is mostly smooth. Some chunks will remain, that’s okay.
Pour 1/2 the batter into the prepared bundt pan and dot with 1/2 of the pureed raspberries. Pour in the remaining batter and dot with the remaining pureed raspberries.
Using a long skewer or a butter knife, swirl the puree dots into the batter to form red swirls throughout.
Place the cake in the oven and bake for 90 minutes, until a toothpick inserted in the center comes out clean.