Heat oven to 180°C/gas mark 4.
Mix the flour and cinnamon with the lime zest in one bowl and the courgette, sugar, oil, and egg in another.
Pour the wet ingredients into the dry and mix gently until combined.
Pour into two 20cm lined tins and bake for 35-40 minutes, until springy to the touch.
Remove from tins and cool completely on a wire rack.
To make the filling, place all the ingredients in a bowl and whisk until light and fluffy.
Sandwich the two cakes together with the filling and then dust the top with a little icing sugar and sprinkle with calendula petals.
