In a large bowl, combine the first 5 ingredients. Combine egg, milk, oil and lemon juice; mix well. Stir into dry ingredients just until moistened. Fold in raspberries and nuts.
Fill greased or paper-lined muffin cups three-fourths full. Sprinkle with sugar. Bake at 400° until a toothpick inserted in center of muffin comes out clean, 18-20 minutes. Cool in pan 5 minutes before removing to a wire rack.
Editor's Note: 1 cup buttermilk can be substituted for the buttermilk blend powder; omit the 1 cup of milk.