Preheat the oven to 170°C fan / 375°F / Gas 5 and line a 900g loaf tin with baking parchment paper.
Zest and juice the orange, reserving 2 tablespoons of the orange juice for the glaze.
In a large mixing bowl, whisk together the eggs, oil, sugar, salt, vanilla, yoghurt, orange zest and juice, until combined and the sugar has dissolved.
Sift the flour and baking powder over the top of the mixture and gently fold in with 2 tbsp of poppy seeds.
Pour the batter into the prepared tin.
Baking: Place in the oven and bake for 55-60 minutes until golden and risen – the cake should split along its top. A skewer inserted into the centre of the cake should come out clean – if it doesn’t, return the cake to the oven for a further 5 minutes and repeat as necessary.
Remove the cake from the oven and allow it to cool in the tin for 6 minutes on a wire rack, then turn out and place back on the rack, over a shallow tray.
Orange glaze: Start with combining 1 tbsp orange juice with the icing sugar, adding more orange juice as needed to get a glaze that is thick but not too runny. Pour the glaze over the warm cake. Remove the tray from underneath the rack and pour any excess glaze back over the cake. Return the tray underneath the cake, then leave the cake to cool completely before serving.