Sauté the onion and green pepper cut into small pieces in a frying pan with two or three tablespoons of extra virgin olive oil. We are stirring until the vegetables are very tender and juicy. Next, add the tuna well drained and crumbled into pieces small in size.
Next, mix well, adding the fried tomato sauce that will help the ingredients to amalgamate. We stir for a few minutes and let the filling cook. Season with salt and pepper and turn off the heat. We let it temper a bit before assembling the lasagna as indicated below.
We soak the lasagna plates following the manufacturer’s instructions. In a baking dish we put a tablespoon of bechamel sauce, -Here you can see how to make it in a simple way- and cover it with a plate of lasagna. On the layer of pasta, we put a couple of tablespoons of the filling and we cover again with another layer of pasta.
We repeat the operation four or five times until we get a kind of a thousand sheets with alternate layers of pasta and filling, ending with one of pasta and covered with a good layer of béchamel. Heat the lasagna in the oven at 190ºC for 15 minutes and then sprinkle with Parmesan cheese, and black pepper and gratin until the surface is golden brown.
Before serving the tuna lasagna let it rest about fifteen minutes to cool slightly, the sauce settles and is easier to cut and distribute. The plate is very hot and will reach the ideal temperature for the diners without the layers of pasta and sauce falling apart.