Grease and line your nonstick 35x25cm (14x10") baking pan. If you don't have any greaseproof paper, greasing and then dusting with flour can help prevent sticking.
Preheat the oven to 180C (160C fan, 350F).
Put the sugar and butter in a large bowl and whisk together until fluffy.
Add the beaten eggs a little at a time and whisk in.
Sift in the flour and fold until smooth.
Add the zest of 4 lemons and the juice of 2 to the mixture and gently mix through.
Spoon the batter into the lined or greased baking pan.
Bake for approximately 45 minutes. The cake should be golden on the outside and the skewer pushed into the very centre should come out clean - keep an eye on it as you don't want it to over-bake.
Make and add the lemon syrup
In a small pan, mix the juice of 4 lemons with the icing sugar.
Place over a medium low heat and stir until the sugar has dissolved, then bring to a boil for 1-2 minutes until you have a light syrupy texture.
Poke holes all over the warm sponge with a skewer, almost down to the bottom.
Take the syrup off the heat (careful, it's hot!) and brush all over the cooling sponge, or pour gradually so that the syrup has time to soak in.
Allow to cool completely, then cut into 12 squares and enjoy with a hot cup of tea or coffee.
Notes
Stored in an airtight container in a cool place out of direct sunlight, your lemon drizzle traybake will keep well for 3-4 days.