cup unsalted butter

Ingredients:
1/2 cup unsalted butter , softened
2/3 cup granulated sugar
1 large egg
1 1/2 teaspoons vanilla extract
1/2 cup milk
1/4 cup plain Greek yogurt , or sour cream
1 2/3 cups all-purpose flour
1 1/2 teaspoons baking powder
1/4 teaspoon baking soda
1/2 teaspoon ground cinnamon
1/2 teaspoon salt
For Topping:
3 Tablespoons butter , melted
1/3 cup granulated sugar
2 teaspoons ground cinnamon