Preheat your oven to 190ºC. Lightly grease and line the oven tin you'll be using for your swiss roll. Something around 30x25 cm would be perfect (the cake pans size is critical for a cake that isn't too thin or thick- mine is on the thicker side, even).
Sift your flour thoroughly to reduce the risk of getting any lumps in the cake batter then set aside in a medium bowl.
Add the eggs to a medium-sized bowl and whisk until the eggs are frothy and pale. Then, add in the vanilla extract and lemon flavor drops and whisk for a further few seconds to fully combine.
Gradually pour in 1/2 cup of sugar, whisking constantly, until you have a pale, glossy batter. Leave the remaining 1/4 cup sugar to one side for now.
Pour this mixture into a large bowl and then fold in the sifted flour carefully. Be careful when doing this as you don't want to knock too much air out of the batter or you won't have a lovely, light and fluffy cake.
Pour the cake mix into your baking tin and use a spatula to help level the mix. I try not to tap it too much for leveling as this can knock out the air. (This is important in having an even Swiss roll).
Bake in the oven for between 10-13 minutes. It needs to be soft, springy, and golden in color. Be very careful not to over-bake as this will ruin your chances of being able to roll it!
Meanwhile, while baking, place a tea towel down on your kitchen surface (optionally, with a layer of parchment paper over it). Sprinkle the remaining caster sugar over this.
As soon as the cake is out of the oven place it face down onto the sugared baking paper/tea towel. Using the tea-towel to stop yourself getting burnt, begin the roll the cake from the short side across.