Preheat oven to Gas Mark 4, 180C. Grease a 9” cake tin. Dust with flour and tap out the excess. Line the base with greaseproof paper.
Sift the flour, baking powder and ginger into a large mixing bowl. Stir in the sugar with a wooden spoon.
Put the eggs, oil, lime zest and juice into a separate bowl and pour over the flour mixture. Stir until well blended. Add to this the grated courgettes, taking care not to over mix. Spoon the mixture into the cake tin and level the surface.
Bake for 45-50 minutes or until a warm skewer inserted comes out of the cake clean. Transfer the tin to a wire rack to cool slightly. Turn out the cake onto the wire rack and leave to cool completely.
For the topping, combine the icing sugar with the lime juice and zest. Spread over the top of the cake allowing it to drizzle down the sides.