Preheat the oven to 180°C/350°F/Gas Mark 4
Method:

Grease a loaf tin and line the bottom with greaseproof paper.

Cream together the butter and caster sugar until pale and fluffy. Add the eggs, one at a time, beating well after each addition, then beat in the lemon zest. Sift in the flour and fold into the mixture, then fold in the ground almonds and lavender flowers. Spoon the mixture into the greased loaf tin and bake in the preheated oven for 40 minutes, until well risen, golden brown and firm to the touch. Remove from the oven and leave to cool in the tin for 10 minutes before turning out onto a wire rack.

For the icing, place the granulated sugar in a small saucepan with the water and heat gently until the sugar has dissolved. Add the lavender and simmer for 2 minutes. Leave the syrup to cool and infuse. Sift the icing sugar into a bowl and strain over the syrup. Mix well, adding more icing sugar or syrup as necessary to achieve the consistency of a thick icing. Drizzle the icing over the cake and decorate with the sprigs of lavender.