Vanilla paste is made by blending concentrated vanilla extract and ground vanilla bean. Its name is a bit misleading, as it is a thick liquid, and not actually paste-like. It is intensely flavorful, and small amounts can be used to substitute for vanilla extract or ground vanilla beans in baking.
In this recipe, if you don't want a very sweet cake, cut the sugar by 1/2 cup. If you want a strong vanilla flavor, add another 1/4 teaspoon vanilla paste.
Preheat oven to 325 degrees. In a large mixing bowl, cream the butter until it becomes smooth. Add sugar in a slow, steady stream and beat until light and fluffy, about 4 to 5 minutes.
Beat in eggs, one at a time, completely incorporating before adding the next egg.
Sift the baking soda and flour together. Add 1/3 of the flour to the butter, sugar, egg mixture.
Add vanilla paste to sour cream. Add 1/2 of the sour cream to the batter and alternate flour with sour cream, with sour cream in two additions. Blend just until smooth.
Pour the mixture into a greased and floured 10-inch tube pan. Bake until the top springs back when pressed lightly and a wooden toothpick inserted comes out clean, about 1 hour 20 minutes.
Transfer cake to a cooling rack. After 10 minutes, invert the pan. Cool completely.
Serve with whipped cream and fruits, chocolate sauce or caramel sauce. If you have extra pound cake left over, toast lightly and serve with lemon curd.