In a large bowl, combine the flour, sugar, baking soda and salt. In another bowl, combine the eggs, sour cream, butter, lemon zest and juice. Stir into dry ingredients just until moistened. Fill greased or paper-lined muffin cups three-fourths full. , In a small bowl, combine flour and sugar; cut in butter until mixture resembles coarse crumbs. Sprinkle over batter., Bake at 350° for 20-25 minutes or until a toothpick inserted in the center comes out clean. Cool for 5 minutes before removing from pans to wire racks. In a small bowl, whisk glaze ingredients; drizzle over warm muffins. Serve warm.