Put the eggs, sugar and lemon zest in a mixer and let the mixer beat for 15 to 20 minutes, until the blend is light yellow and three times the original volume.
Remove the bowl from the mixer and sprinkle the flour partially, while mixing with a spatula until fluffy.
Preheat the oven to 170ºC.
Grease a spring tin and line it with baking paper.
Pour the batter into the tin and put it in the oven.
Bake for 35 to 40 minutes and leave the oven closed for the first 30 minutes. With a satay prick you can check if it's cooked. If the prick is still damp, let it bake for a while.
When the cake is cooked, turn off the oven and leave the oven door ajar. Let it cool down for 10 minutes. Then place the cake on a grid to continue to cool. After 10 minutes, gently loosen the cake with a knife, remove from the spring tin and leave to cool down.