Pre-heat oven to 375F and line the muffin tin with 12 paper liner or spray with oil.
For Stresuel topping
First make streusel with softned butter, flour, lemon zest and sugar and set aside.
For muffins
In a medium bowl, mix, flour, salt, baking powder baking soda , poppy seeds and sugar and set aside.
Large bowl, add melted butter, egg, lemon juice, lemon zest milk and sourdough starter and mix well.
To this add dry ingredients and mix well.
Transfer to muffin tin lined with papper liner
Then divide and add streusel top of muffin dough.
Bake at 375°F for 17- 18 minutes or until toothpick comes out clean.
Cool completely in a cooling and rack.
If you want you can brush with lemon juice on the warm muffins.
Enjoy with cup of coffee for your breakfast or as snack.