Brown the sausage and onion.
Add the Italian sausage to a large skillet and cook for a couple of minutes. Stir in the diced onion and continue cooking until the meat is browned and the onion has softened.
Build the sauce.
Add the crushed tomatoes, water, Italian seasoning, sugar, garlic powder, and salt. Stir well and bring the mixture to a boil.
Add the noodles.
Break the uncooked lasagna noodles into roughly 1-inch pieces and stir them into the sauce. Cover the skillet with a lid.
Cook until tender.
Let the mixture boil for 18 to 20 minutes, stirring often, until the noodles are tender and the sauce has thickened.
Finish with cheese.
Spoon dollops of ricotta over the top, then sprinkle on the mozzarella. Remove the skillet from the heat.
Let it rest.
Cover the skillet again and let it sit for a few minutes so the cheese melts and the lasagna settles slightly.
Garnish and serve.
Top with Parmesan and parsley if you like, then scoop and serve warm.