In a large bowl, combine flour, sugar, baking powder, baking soda and salt.
Combine eggs, yogurt, oil and lemon zest; mix well. Stir into dry ingredients just until moistened. Fold in raspberries.
Fill greased or paper-lined muffin cups three-fourths full. For topping, combine sugar and flour. Cut in butter until mixture resembles coarse crumbs; sprinkle about 1 tablespoon over each muffin.
Bake at 400° for 18-20 minutes or until muffins test done. Cool in pan 10 minutes before removing to a wire rack. (Some reviewers suggested lowering temp to 375. I would do so after the first 5 minutes because the initially higher heat causes the muffins to rise more.)