Apple-Cinnamon Coffee Cake | America's Test Kitchen

Ingredients

• 1 tablespoon unsalted butter
• 2 Granny Smith apples , medium-large, peeled and cored, cut into 1/4-inch dice
• 1 1/4 cup granulated sugar
• 2 cups unbleached all-purpose flour
• 2 teaspoons ground cinnamon , divided
• 1 teaspoon table salt
• 10 tablespoons unsalted butter ( 1 1/4 sticks), softened
• 1 teaspoon baking powder
• 1/2 teaspoon baking soda
• 3/4 cup buttermilk (or low-fat plain yogurt)
• 1 large egg , at room temperature
• 1 teaspoon vanilla extract
• 3/4 cup walnuts (or pecans), finely chopped (about 3 ounces/85 grams)
• 1/2 cup packed dark brown sugar