Layer lasagne noodles in the bottom of the dish, overlapping them slightly so there are no gaps in between. If you're using the small, no-boil kind like I did, you'll need around 5-6 noodles in each layer. If you're using the regular lasagne noodles, you will need to layer them lengthwise, in which case you'll need around 4 in each layer.
Roast bell peppers directly on an oven rack, with the oven preheated to 350 degrees. Turn occasionally until the skin has charred and wrinkled uniformly all around the pepper. Remove, and when the peppers are cool enough to handle, peel off the skin and discard along with the seeds and stalk. Chop into thin strips and put in a bowl.
Slice eggplant into 1/3-inch-thick slices, set the slices down on a lightly oiled baking sheet. Sprinkle salt and pepper on the slices and drizzle a little bit of olive oil on each. Place under the broiler and let the slices broil for three minutes until they are turning golden. Flip the eggplant slices and broil another three minutes until the eggplant is quite tender. When cool enough to handle, slice the eggplants and place in the bowl along with the peppers.
Halve the beefsteak tomatoes. Place the tomatoes, cut side up, on a lightly oiled baking sheet. As with the eggplants, season with salt and pepper and drizzle some olive oil on the tomatoes. Bake in a 425-degree oven for about 30-40 minutes or until the tomatoes are turning golden and are quite soft. Remove, slice when cool to the touch, and add to the bowl containing the other roasted vegetables.
For the Sauce: Saute onion in olive oil till translucent, add the thinly sliced cloves of garlic, 1 - 12-oz package extra-firm tofu,2 handfuls of baby spinach for few minutes. Let it cool and blend them together
Spread one-third of the tofu-spinach sauce evenly on the lasagne noodles.
Now layer one-third of the roasted vegetables on top of the sauce, spreading them evenly.
Spread a small handful of the crumbled vegan mozzarella, if using, on top of the vegetables.
Now add another layer of noodles, and repeat the layering process with the sauce, the vegetables and the cheese. (You should end up with four layers of noodles, and three layers of vegetables and sauce.)
By the time you get to the fourth layer of lasagne noodles, you will be out of the sauce and roasted vegetables. Crumble the remaining mozzarella cheese evenly over the top. You can also sprinkle on 1 cup of breadcrumbs (optional. I didn't use any).
Cover the lasagne pan with aluminium foil.
Bake in a 375-degree oven for 40 minutes.
Now remove the foil and continue baking for another 5 minutes or until the cheese on top gets bubbly and starts to turn golden.
Remove and let stand for a few minutes before cutting in.