1.Grease 23cm-square slab cake pan, line base with baking paper.
2.Beat egg yolks, sugar and rind in small bowl with electric mixer until changed to a lighter colour. Gradually add ouzo, beating until just combined.
3.Transfer mixture to large bowl, stir in juice, semolina and nuts; cover, stand 30 minutes. Beat egg whites in small bowl with electric mixer until firm peaks form, fold gently into cake mixture, in two batches.
4.Pour mixture into prepared pan. Bake in moderately hot oven about 20 minutes. Pour warm Syrup over warm cake in pan; cool in pan.
5.Syrup Using a vegetable peeler, cut rind thinly from lemon, avoiding white pith. Cut rind into thin strips. Combine sugar, the water, juice and rind in small saucepan; stir over heat, without boiling, until sugar dissolves. Simmer, uncovered, without stirring, 5 minutes; cool 10 minutes before using.