Preheat oven to 350 degrees F and grease a 9x9-inch baking dish.

In a large mixing bowl, add sugar and melted butter. Mix for 1 minute or until light and airy.

Add eggs one at a time, followed by the vanilla extract.

In a small bowl, sift together the flour, baking powder, and salt. Slowly add dry mixture to the wet ingredients until just combined.

Fold in sour cream.

Transfer batter to the prepared baking dish and sprinkle remaining granulated sugar on top.

Bake for 30-35 minutes or until an inserted toothpick comes out clean.

Allow cake to cool before slicing.