Preheat the oven to 180C (160C fan, 350F). Put the sugar and butter in a large bowl and whisk together until fluffy.
Add both eggs and whisk in.
Sift in the flour and fold until smooth.
Add the zest of two lemons and the juice of one to the mixture and gently mix through.
Spoon the batter into a greased and lightly floured cake tin. I recommend using a nonstick loose-bottomed or springform tin as it makes it super easy to get your cake out of the tin cleanly.
Bake for 25-30 minutes. (The wider the cake tin, the quicker it will cook). The cake should be golden on the outside and the skewer should come out clean - keep an eye on it as you don't want it to over-bake.
In a small pan, mix the juice of two of the lemons with the icing sugar.
Place over a medium heat and stir as it heats, continuing until you have a 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 pour all over the cooling sponge.
Allow to cool, then cut into generous slices and enjoy with a hot cup of tea or coffee.
Stored in an airtight container in a cool place out of direct sunlight, your lemon drizzle cake will keep well for 3-4 days.