Cinnamon-Buttermilk Muffins

INGREDIENTS

• 7 Tbs. unsalted butter, at room temperature
• 2/3 cup sugar
• 1 egg
• 1 1/2 cups all-purpose flour
• 1 1/2 tsp. baking powder
• 1/2 tsp. baking soda
• 1/2 tsp. salt
• 1/2 tsp. freshly grated nutmeg
• 1/2 cup buttermilk
• 1 1/2 tsp. vanilla extract
• 1 Tbs. ground cinnamon
• 6 Tbs. (3/4 stick) unsalted butter, melted