Good-Cooking - Rhubarb Ripple Coffee Cake

Ingredients

• 1 1/3 cups rhubarb puree or sauce (see rhubarb puree recipe)
• 2 1/4 cups unbleached all-purpose flour
• 3/4 cup granulated sugar
• 3/4 cup (1 1/2 sticks) unsalted butter
• 1 teaspoon baking powder
• 1/2 teaspoon baking soda
• 1/2 teaspoon cinnamon
• 1 tablespoon orange zest, finely minced, or 1/4 teaspoon orange oil
• A heaping 1/4 teaspoon salt
• 1 beaten egg
• 1 teaspoon vanilla extract
• 3/4 cup buttermilk or sour milk *
• Confectioners' sugar for dusting