My dh's Spinach lasagne is a almost the only vegetarian lasagne I can tolerate. My mother's authentic meat version is to die for and I'm afraid I was spoilt by it.
Dh's version (serves about 4)
I large pot of plain yoghurt (are they 500g??)
Sour cream (if you want it) - about 50g
Cheese (cheddar but you can use parmesan) about 200g
Spinach (as much as you want - this tends to vary as to how much we have in)
1 onion
lasagne sheets (pre-cooked ones or fresh)
Tomato sauce (preferably home-made but if using jars use 11/2 large jars)
Fry onions gently in the butter with herbs Cook spinach, drain well and chop (can use frozen if easier)
Mix spinach with onion mix, yogurt, cheese and sour cream (if using)
Alternate layers of lasagne, white/spinach mix and tomato sauce. Finish with a sprinkle of parmesan cheese
Cook in oven for about 40 mins (190oC)
It comes out surprisingly firm (one of my real bugbears is that awful bastardised sloppy mess of a lasagne that you get in lot of places)
Also it is different enough from a normal meat lasagne to not be 'trying' to be one. also it is incredibly easy to make.