Lasagna usually involves lots of pots and pans but this one is incredibly easy because it all comes together in one skillet. Need I say more?
Technique tip: If you don't enjoy the bitterness of broccoli rabe, you can blanch it and shock it before adding it into the pan to take away a bit of that bite.
Swap option: Broccoli rabe can be replaced with regular broccoli if preferred. Just cut it into small florets.
Preheat oven to 375 degrees. In a 12-inch, high-sided skillet, heat oil olive over medium heat. Add the sausage and cook for about 7 minutes, breaking it apart into bite sized pieces with a wooden spoon, until cooked through and brown.2.
Add the shallots and garlic and cook for 3 minutes, or until translucent and slightly fragrant. Add lemon zest and red pepper flakes and cook for an additional 2 minutes to toast. Stir in broccoli rabe and season with salt. Cook for 2 minutes or until rabe is wilted. Remove the meat mixture a medium bowl and return the pan to low heat.3.
Spoon a small amount of the marinara sauce on the bottom of the skillet. Mix the remaining marinara with the sausage mixture in the bowl.4.
Layer half the lasagna noodles on top of the marinara breaking them up as needed to fit the pan. Cover with half of the meat mixture. Add 3/4 cup Parmesan cheese and half the mozzarella. Layer the remaining noodles. Cover again with remaining sauce and top with the remaining Parmesan, mozzarella and Gruyere.5.
Bake for 40 minutes or until the top is golden and bubbly. Let the dish cool for 5 minutes before serving.