Coat berries in 1 Tbsp flour, take flour from the flour you measured out to bake muffins.
Preheat oven to 425 deg F and line a 6 count muffin pan with liners or spray it with a non stick spray and set it aside.
Whisk egg, sugar, buttermilk, vanilla, oil and lemon zest (if adding) together in a medium mixing bowl.
Sift flour, baking powder and salt over wet ingredients. Fold in berries next. Take care not to over mix the batter.
Pour batter in the prepared muffin pan and top with streusel Topping.
Bake at 425 deg F for 5 minutes and then keeping the muffins in the oven, reduce the temperature to 350 deg F.
Continue to bake for 13-20 minutes or until they pass tooth pick test. Keep an eye on them, do not over bake.
Allow to cool for 5 minutes in the pan and then transfer to wire rack to finish cooling.