Preheat oven to 350 degrees F. Grease bottom and 1-inch up side of a 9x5x3-inch loaf pan. In a large bowl combine 2 cups flour, the baking powder, baking soda, cinnamon, and salt. Make a well in the center and set aside. In a small bowl toss chopped plums with 1 tablespoon of flour; set aside.
In a medium bowl combine sugar, oil, eggs and vanilla. Pour into the well in the dry ingredients and stir until moistened (batter will be very thick). Fold in plums and spoon into prepared pan. Bake 60 to 65 minutes or until a toothpick inserted near center comes out clean.
Cool in the pan 10 minutes. Remove from pan and cool completely on a wire rack. Glaze with Lemon Glaze just before serving. Makes 8 servings.
In a medium bowl whisk together powdered sugar, lemon juice, and enough milk to make a glaze-like consistency. Makes 1/4 cup.