For Assembling, Topping and Serving:
Boil lasagna noodles if needed, according to package instructions, and set aside.
Preheat the oven to 450°F. To make the vegetable filling, remove the stems and clean out the insides of the bell peppers. Pour in 1 teaspoon olive oil and swirl to coat. Pour any leftover oil into your hand and rub on the outside of the peppers. Place peppers in a baking dish and roast until blistered and blackened in places, 30 to 40 minutes. When done, remove from the oven and cover tightly with parchment paper and foil and set aside.
Meanwhile, add 1 teaspoon olive oil to a saucepan or skillet over medium high heat. Add onions and cook for 1 minute. Add garlic and cook for 1 minute more. Transfer to a bowl and set aside.
Add spinach and artichokes to the same pan and cook for 3 minutes. Lower heat to medium-low, then add the onion-garlic mixture back to the pan along with the red pepper flakes, 1/2 teaspoon salt, pepper and 1 teaspoon of the thyme.
Remove the parchment paper and foil from roasted bell peppers. Peel the skin from the peppers. Chop peppers and add to the pan. Stir to mix well, then cover and remove from the heat.
To make the marinara sauce, put diced tomatoes, tomato sauce and tomato paste in a saucepan over medium heat. Stir to mix well. Lower heat once the sauce starts to bubble. Stir in oregano and remaining 1/4 teaspoon thyme. Cover and remove from the heat.
To make the cashew ricotta, drain the soaked cashews and put them in a food processor. Add almondmilk, garlic, remaining 1/2 teaspoon salt, nutritional yeast, basil and lemon juice. Blend all ingredients together until very smooth. Spoon into a bowl and set aside.
Preheat the oven to 375°F. To assemble the lasagna, lightly coat a 9x13-inch baking dish with olive oil. Spread a thin layer of marinara sauce on the bottom of the baking dish. Arrange a layer of noodles on top of the sauce. Spread with half of the cashew ricotta, followed by half of the spinach mixture. Top with half of the marinara sauce. Repeat with remaining noodles, cashew ricotta, spinach mixture and marinara. Finish with a layer of noodles.
Top noodles with zucchini, making sure to cover noodles as completely as possible. Brush with olive oil and sprinkle with Italian seasoning. Cover with foil and bake for 50 minutes, then uncover and bake 10 minutes more, until noodles are tender. Let lasagna stand for 10 minutes. Cut into squares and serve topped with basil.