Preheat your oven to 350 degrees and line your muffin tins with your liners.
In a large bowl sift the flour, sugar, baking powder, baking soda, and salt and mix.
In another bowl, mix the buttermilk, butter, lemon zest, and eggs.
Make a hole in the center of the dry ingredients and pour the wet ingredients into the dry ingredients. With a spatula or fork fold the mixed batter just until it is incorporated. Remember not to over mix!
Fold in the fruit, in this case blueberries..
Scoop the batter into the cupcake liners and top with streusel topping.
Bake the muffins for 20 to 25 minutes, until cooked through and golden brown. Serve warm with salted butter on the side.