Lemon Blueberry Muffins

All purpose flour-2

Sugar-3/4

Baking powder-2

Baking soda-1

Salt-1/2

Butter-1/2 cup/125

Plain yogurt-1 cup/250

Egg-2 large

Milk-

Vanilla essence-

Lemon- zest of one lemon and juice of 1/2

Blueberries (fresh or frozen-1 cup)

Demerara/Turbinado sugar for sprinkling (optional)