Preheat the oven to 190°c (170 fan/ 375F/ Gas 5). Place 12 muffin cases in a 12 hole muffin tin.
Mix the dry ingredients together in a large bowl (plain flour, caster sugar and bicarbonate of soda).
In another bowl whisk together the yogurt, eggs and cooled melted butter.
Gently mix the dry ingredients with the wet ingredients until combined (be careful not to over mix).
Fold in the lemon zest.
Place 1 tablespoon of the batter into each muffin case. Top with 1 teaspoon of lemon curd.
Spoon over the remaining muffin batter and bake for 18 minutes.
Whilst the muffins are in the oven, mix together the caster sugar and lemon juice for the drizzle icing.
Take the muffins out of the oven and immediately spoon over the lemon drizzle.
Leave to cool for 30 minutes before eating.