Grate the carrots into a bowl. Add in the mushrooms. Season with salt, pepper, and cayenne / red chili powder if desired.
Mix in one bottle of pasta sauce. Set aside.
Cut the zucchini lengthwise into slices of even thickness. You want these to resemble the noodles.
Place the slices on a paper towel to absorb excess moisture. Season with salt and pepper.
In a pan over medium heat, sauté the onions in 1 tbsp of olive oil until golden.
Stir in the flour to build a blonde roux. This will thicken up the sauce and help the lasagna set.
Add in the ricotta and stir continuously to make sure nothing sticks and the flour doesn’t burn.
Add in the spinach. Cook until wilted.
Season with salt, pepper, and a pinch of nutmeg.
Boil noodles per package instructions. After they are cooked, run under cold water so they don’t stick.
Assemble the lasagna! Start by spraying a pan with olive oil so the pieces are easy to take out. Lay one layer of the lasagna noodles on the bottom. Top with a cup of pasta sauce and a cup of mozzarella. Layer about a half of the carrot mushroom mixture on top.
Add another layer of pasta noodles, this time perpendicular to the pattern in the first layer. I’ve found that this helps to stabilize the lasagna when cutting.
Add in about half of the spinach ricotta mixture. Spread evenly.
Top with the zucchini slices as if they were a layer of noodles.
Repeat the steps until you’re out of ingredients.
Top the lasagna with the remaining cheese.
Cover the pan with foil and put in a 350 degree oven for 2 hours.
If you are serving immediately, turn up the heat to 400 degrees and remove the foil. This will help make the cheese golden brown. If you are waiting to serve, perform this step during the reheating process.