Start by trimming the ends off the zucchini. Slice the zucchini into strips ~1/8th inch thick. Place the zucchini slices in a single layer on paper towels. Season generously with Himalayan salt and let air dry for at least 4 hours. The salt will help draw out the moisture.
When about half of the meat is browned, add the chopped onions and diced tomatoes. Cook for 2-3 minutes to cook off the excess liquid.
Add the minced garlic, oregano, thyme, parsley and basil to the meat. Cook until the meat is no longer pink, another 5-8 minutes. Transfer the cooked bison to a heat proof bowl and wipe the skillet clean. Let the bison cool.
Reduce the heat to medium. Coat the skillet with olive oil then add the mushroom slices. Saute for 2-3 minutes, until the mushrooms are starting to lose their moisture.
Add an additional tablespoon of olive oil to the skillet. Then add in all of the spinach and stir constantly until the spinach is completely wilted and dark green. Set aside to cool.
Meanwhile, use a paper towel to blot off the water from the zucchini. Soak up as much of the liquid from the zucchini as you can.
In a 9x9 casserole dish, spread the marinara across the bottom in a light but even layer. Use a spoon to spread the marinara to the edges of the dish.
In the bowl with the cooked bison mixture, stir in one egg, ½ cup parmesan cheese, ½ cup mozzarella cheese and ¼ cup ricotta cheese. Stir until well combined.
Begin assembling the zucchini roll-ups: first, spread some of the sauted spinach and mushrooms down the center of the zucchini slice. Do not over load the zucchini.
Use about a tablespoon or two of the bison mixture and spread it down the middle of the zucchini slice. Roll the zucchini slice, starting with the edge closest to you and use your hands to press the sides of the zucchini in to prevent any filling from coming out.
Arrange the rolled zucchini into the baking dish with the marinara. Repeat until you’ve filled the baking dish – the zucchini rolls should be close together but not overcrowded.
Spread the remaining ricotta over the top of the zucchini rolls followed by the remaining parmesan and mozzarella, as desired.
Bake at 375 F (190 C) for 30-40 minutes uncovered. Let the lasagna set for 10-15 minutes prior to serving. Serve with extra parmesan cheese and a basil leaf for garnish. Enjoy!