Plum Streusel Coffeecake

INGREDIENTS

• 3/4 stick (6 tablespoons) unsalted butter, cut into pieces and softened
• 2 large eggs
• 1/2 teaspoon salt
• 1/2 cup walnuts
• 1/2 cup firmly packed light brown sugar
• confectioners' sugar for sifting over cake
• 1 teaspoon cinnamon
• 3/4 cup granulated sugar
• 1 1/4 cups all-purpose flour
• 1/4 teaspoon freshly grated nutmeg
• 1 stick (1/2 cup) unsalted butter, softened
• 1 teaspoon baking powder
• 3/4 pound plums (4 to 5 medium), sliced
• 1 cup all-purpose flour
• 1 teaspoon vanilla