Preheat your oven to 375ºF and spray a 12-muffin tin with cooking spray.
Meanwhile in a small bowl combine the flour, sugar, pinch of salt and melted butter with a fork. The topping should be chunky. Set aside.
For the Muffins
In a bowl whisk the eggs until frothy, about 3-4 minutes. Add in the sugar and oil and whisk until combined. Add in lemon zest, juice, vanilla and stir to combine. Whisk in sour cream.
In a separate bowl whisk together the baking soda, salt and flour. Pour the wet ingredients on top of the dry and stir with a spatula or wooden spoon to combine.
Fill the muffin tins about 3/4 full and top with the topping.
Bake until a toothpick inserted comes out clean, about 18-22 minutes. Cool about 5 minutes then remove muffins from the tin and cool completely.
For the Glaze
In a small bowl combine the powdered sugar and lemon juice and whisk together. If the glaze seems too stiff add in more lemon juice. Drizzle over the muffins. Serve.