Preheat the oven to 180 C / Gas 4. Line a 900g loaf tin with baking parchment.
Combine the margarine and sugar in a mixing bowl and beat until light and fluffy. Add the eggs, one a time, beating well after each addition until pale and creamy. Fold in the flour, baking powder and zest until well integrated. Spoon into the prepared loaf tin.
Bake in the preheated oven for 35 to 45 minutes until risen and golden and a skewer inserted into the centre comes out clean.
For the drizzle:
Mix the lemon juice and sugar together as soon as your cake is in the oven and leave to stand.
Remove the cake from the oven and while warm and still in the tin, make holes with a skewer and pour over the drizzle. Leave the cake to cool in the tin so the lemon sugar can be absorbed. Remove from the tin, discard the baking parchment, slice and serve.
Try to achieve a weight as close to 225g for the eggs as possible. You can always remove a little of the egg if you go over.