Beat the butter and sugar with an electric mixer until pale and smooth. Add the vanilla extract and eggs one at a time, mixing with each addition.
In a separate bowl, combine the flour, baking soda and salt. Add this to the batter in 2 additions, alternating with the sour cream.
Generously spray both sides of a lamb cake pan with cooking spray. You want to make sure that you grease every crevice, so that nothing sticks to the pan! Place a spoonful of flour into each pan and shake it around the pan until it is evenly coated in flour. Tip the pans over and tap them a couple times to remove any excess flour.
Pour the cake batter into JUST the pan with the lamb’s face/front. Start with adding just a couple dollops to the lambs face, tap the cake pan on your counter a couple of times to remove any trapped air, then add the rest of the batter. Place the second pan/lamb’s back on top of the filled pan. You will see a vent at the back of the lamb’s head. This is so that steam can escape while baking.
Transfer the lamb to a baking sheet and bake at 350F for 45-60 minutes, or until a skewer inserted into the cake comes out clean. Cool for 15 minutes in the pan, then turn out onto a wire rack and cool completely.