Add the ground beef to a large skillet set over medium-high heat. Cook the beef, stirring often, for 5-8 minutes or until it is browned. 

Remove the beef to a bowl and discard any grease. No need to clean or wipe the pan-- just make sure to get rid of any extra fat. 

Place the pan over medium-high heat again and add the olive oil. Add the onion and cook, stirring occasionally, for 5 minutes or until it is soft and just starting to brown. 

Add the garlic and tomato paste and cook for 1 minute. 

Next, add the beef back to the pan along with the crushed tomatoes, salt, and red pepper flakes, if using. 

Bring the mixture to a simmer and then stir in the basil. Remove the pan from the heat and set it aside to cool. 

In a small bowl, combine the ricotta, mozzarella, parmesan, and salt. Set aside until ready to use. 

Preheat your oven to 375ºF. 

Bring a pot of salted water to a boil. 

Cook the lasagna noodles to two minutes less than al dente (make sure to look at the time on the box-- it will vary by brand). Drain the water and rinse the noodles under cold water to stop the cooking. 

Lightly grease a 9x13-inch pan with olive oil or butter. Add 1/5 of the sauce (about ½ cup) to the bottom of the pan and spread it out so the bottom is fully covered. 

Top with the remaining sauce and then sprinkle over 1 cup of mozzarella cheese.