Sourcream cake

1/2 cup unsalted butter (cold and cut into 1/2-inch cubes)
1/4 cup light brown sugar (packed)
1 cup all-purpose flour
1/2 tsp baking soda1/2 tsp salt

3/4 cup unsalted butter
2 cups all-purpose flour
11/2 tsps baking powder
1 tsp ground cinnamon
1/4 tsp baking soda
1/2 tsp salt
1 pinch nutmeg
1/2 cup granulated sugar
1/2 cup light brown sugar (packed)
2 large eggs
11/2 tsps vanilla extract
1/2 cup sour cream