Using a mandolin, slice the zucchini into long, thin slices.
Spray a 7-inch springform pan with oil and arrange the zucchini in overlapping layers in the bottom of the pan.
Place 1/4 cup of marinara sauce on top of the zucchini and spread evenly.
In a large bowl, mix the onions, garlic, and Italian sausage. Layer the meat on top of the zucchini and spread evenly.
Pour the rest of the marinara sauce and spread it evenly.
Rinse the bowl you used earlier, and mix together the ricotta and mozzarella and 1/4 of a cup of the Parmesan cheese.
Spread the cheese mixture on top of the meat.
Top with the remaining 1/4 cup parmesan cheese.
To recap, the layers are: zucchini, sauce, meat, sauce, cheese mix, parmesan cheese.
Cover the pan with foil or a silicone lid.
FOR THE OVEN
Bake at 350 for 35 minutes, then remove foil and cook for an additional 10-15 minutes.
Allow the lasagna to rest for 10 minutes before unclasping the springform pan to serve.
FOR THE AIR FRYER
Set the air fryer to 350F and bake for 20 minutes. Then, remove the foil and cook for another 8-10 minutes at 350F until the top is browned and bubbling.
Allow the lasagna to rest for 10 minutes before unclasping the springform pan to serve.
Foil. Don't skip the foil step, or your cheese won't be as bubbly and delicious.
Fit. Make sure your spring-form pan fits in your Air Fryer (if that's what you're using) before you add all the ingredients.
Cool. Make sure to wait 10 minutes after cooking to release it from the spring-form pan and slicing it, or your Keto Lasagna will fall apart.