In a large bowl, combine the flour, sugar, baking soda and salt. In another bowl, combine the eggs, sour cream, butter, lemon zest, juice and extract. 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 pat down slightly then add a little more over top.
Bake at 350° for 18-22 minutes or until a toothpick inserted in the center comes out clean. Be sure not to over-bake. Cool for 5 minutes before removing from pans to wire racks.
Whisk the glaze ingredients in a small bowl and drizzle over warm muffins.
Notes
When adding crumb topping add a little to each muffin cup and pat down. Then add a little more on top. This gives you a base layer that sticks a bit better and adds room for more crumb topping! Pay attention to the measurements requiring 2 measurements of an ingredient.