Susan's new fave blueberry muffins

Blueberry Streusel Muffins (one dozen)

Streusel (This will be enough for 36 muffins, if yours are like mine!)
1 ¼ c flour
1/3 c brown sugar, packed
1/3 c sugar
½ tsp cinnamon (use more!)
7 tbsp butter, melted

Muffins
2 c flour
1 egg
1 t vanilla
1 tsp lemon zest (I used a few drops of lemon extract)
1 c sugar
4 Tbsp melted butter, slightly cooled
½ c buttermilk
1 tbsp baking powder
1 ½ c frozen blueberries, dredged in 1 Tbsp of the flour

   Toss streusel ingredients with fork until crumbly.  Whisk egg, add vanilla, sugar, and lemon zest until combined.  Slowly add melted butter, then whisk in buttermilk.  Add remaining dry ingredients and stir until almost mixed.  Fold in dredged blueberries (dredging keeps the batter from turning purpley gray!).  Divide in 12 greased muffin cups and top with streusel...use a canning funnel, and all the streusel will stay on the muffin tops instead of getting all over the pan.  375º, 23-27 minutes.  Cool in pan 20 minutes.  Will keep in airtight container about 3 days.