1. For the cashew ricotta: Heat enough water to cover cashews. The water should be hot but not quite boiling.
2. Pour water over cashews in a bowl. Cover and allow to soak for at least 30 minutes or up to overnight.
3. Drain cashews and place into food processor. Add remaining ingredients and process into a smooth paste, scraping down sides of bowl, frequently.
4. The texture will be very similar to ricotta. Add water, a tablespoon at a time if needed, to attain desired texture. Set ricotta aside.
5. For the noodles: Wash zucchinis and cut off ends.
6. If you have a mandolin slicer, use it to cut the zucchini into lasagna 'noodles'.
7. Otherwise, using a sharp knife, cut the zucchini as thinly as possible length-wise into lasagna 'noodles'.
8. Place noodles in a colander and salt generously. Toss with hands to make sure salt is evenly distributed.
9. Place colander over a bowl or in a sink and allow to drain while you make the filling.
10. For the filling: Preheat oven to 350F. Spray a 13x9 baking pan with cooking spray.
11. Peel, quarter, and thinly slice onions. Drain diced tomatoes.
12. In a large soup pot, heat olive oil on medium heat and then sauté the onions until translucent.
13. Add ground beef, sausage, garlic, oregano, basil, red pepper flakes, and sea salt, and brown the meat.
14. Add diced tomatoes and tomato paste and combine well.
15. Place zucchini in a clean dish towel and gently press out any remaining water, trying not to break the noodles. Pat zucchini as dry as possible.
16. In prepared baking dish, form a single layer of zucchini noodles. Place noodles at each end of pan to form a collar to help hold in filling.
17. Ladle 1/3 of the meat mixture on top and spread sauce to cover zucchini.
18. Top with another layer of sliced zucchini and another 1/3 of the meat mixture.
19. Top meat sauce with cashew ricotta. Using a spatula, gently spread ricotta over meat mixture.
20. Top with remaining zucchini noodles and then remaining meat mixture.
21. In a small bowl, beat eggs until uniform. Pour beaten eggs evenly over the dish. Use a spatula to spread eggs over top of lasagna.
22. Gently run spatula around edge of lasagna, allowing egg to drip down the sides as well.
23. Cover the lasagna with a layer of parchment paper, then a layer of aluminum foil to prevent leaking of aluminum into your food.
24. Place baking dish on a parchment-lined jelly roll pan (in case the lasagna bubbles over).
25. Bake for 45 minutes. Allow to cool slightly (10-15 minutes) before serving.