Preheat oven to 350 degrees Fahrenheit.
Grease a loaf tin.
Add butter and sugar to a bowl or mixer. Mix until light and fluffy (the longer, the lighter the sponge).
Break the eggs into a small blender, add the minced jalapeño and blend until smooth.
With the mixer on a very low speed add a tablespoon of the egg to the cake batter then turn the speed up to incorporate air into the mixture.
Repeat until all of the egg is used up.
Take the bowl off the mixer and grate the zest of the lemons into the mixture (keep the lemons to use the juice in the drizzle.)
Add the baking soda and flour.
Fold very gently until the ingredients are combined.
Transfer the mixture gently into the loaf tin being careful not to knock any of the air out.
Bake in center of the preheated oven for around 25 minutes (checking after 20.)
Remove from the oven and allow to cool for 5 minutes before transferring the cake to a wire rack
While cooling, squeeze the juice from the lemons and combine it with the powdered sugar.
Use a fork to prick the top of the cake repeatedly to allow the drizzle to penetrate.
Drizzle half of the icing over the cake and leave for 5 minutes.
Repeat with the second half and your cake is complete.
Feel free to grate some more zest on top and perhaps some candied jalapenos for decoration.