Take a pan (preferably 7 by 3 inch) and layer the ingredients of lasagna.
Break the oven ready lasagna noodles to the bottom of the pan.
Start with a layer of marinara sauce.
Top with half ricotta cheese mixture.
Top with meat and onion mixture.
Add marinara sauce on the meat.
Add another layer of lasagna layer and repeat the process.
After repeating all the steps and final layer of lasagna noodles.
Top it with tomato sauce and mozzarella cheese.