Prepare the lemon cake in 3 round pans--according to directions. Be sure to level the pans before baking as you don't want a mounded top.
Prepare the lemon pie filling according to the box directions. (You can make your own-but this is good and easier). Set aside to cool.
Separate the rest of the eggs and beat the whites (as well as the whites left from the pie filling)for meringue adding a pinch of cream of tarter and the sugar.
When the cake has cooled, place one layer on an ovenproof dish. Spoon half of the pie filling on the layer, add the next layer and the rest of the filling and then top with the final layer. Cover with the meringue. Place in a hot oven --around 450* and just toast the meringue.