Divide the broccoli into florettes and place into a pot of boiling water, cook until tender.
Place the butter, flour and milk into a saucepan, heat stirring continuously until sauce thickens and comes to the boil.
Remove from the heat, add the flaked salmon, broccoli, lemon rind, juice and seasoning to taste.
Place half the mixture into the base of a rectangular ovenproof dish 10"x8" place a layer of lasagne sheets on top, repeat finishing with a layer of lasagne sheets.
Whisk together the egg, yogurt, and cheese, pour over the lasagne and bake in the oven for 25 minutes.