Zest one organic lemon and scrape the grated peel in a bowl with the sugar. Add one tablespoon of finely chopped fresh rosemary. Stir to infuse the flavour and let it rest for one hour.
Whip the eggs with the aromatic sugar until foamy and white. Add the olive oil and the juice of half a lemon, then whisk gently.
Sift the spelt flour, baking powder and salt and incorporate delicately into the batter.
Butter and dust with flour a 22cm round baking tin before tipping in the batter.
Heat the oven to 190°C and bake the cake for about 35-40 minutes, until it is golden brown and cooked through.
Cool completely before turning into a plate.
Crush the sugar and the rosemary flower in a mortar to release the rosemary essence and sprinkle over the cake.