Preheat the oven to 220°C/425°F/gas mark 7. Line a 12 cup muffin tray with muffin liners.
In a large bowl, whisk together the flour, baking powder, bicarbonate of soda and salt until very well combined.
In a large jug, whisk together the sugar, eggs, lemon zest, lemon juice, melted butter, yogurt and vanilla extract until smooth.
Add the liquid ingredients to the dry along with the poppy seeds and fold together gently until just combined. There should be no pockets of flour left but be careful not to overmix.
Divide the mixture evenly amongst the muffin liners, I use a trigger ice cream scoop to do this.
Bake for five minutes then without opening the oven door, turn the temperature down to 190°C/375°F/gas mark 5 and bake for a further 10-12 minutes until golden and a skewer inserted into the centre comes out clean.
Transfer the muffins to a wire rack and leave to cool completely.
To make the glaze, sift the icing sugar into a small bowl and gradually stir in the lemon juice until it is thin enough to drizzle.
Drizzle the glaze over the tops of the muffins and serve. Best eaten on the day they are made but will keep in an airtight container for a couple of days.