Preheat the oven to 425° F (218° C). If using pizza cheese sauce, make it now and set it aside.
Prep the Zucchini
Wash the zucchini and slice them in half the long way. Cut a border around the zucchini about 1/4 inch in from the edge. With a spoon, scrape out the inside of the zucchini and place the scrapings in a small bowl. Chop it up into small pieces and sprinkle it with salt, and let it sit for about 10 minutes.
Place your zucchini halves on a parchment-lined baking sheet and brush with olive oil. Then bake the empty zucchini halves for 15 minutes at 425° F (218° C).
Make the filling
While the zucchini is baking, sauté a diced onion and garlic in olive oil over medium-low heat. Sprinkle with 1/2 tsp of salt, Italian herbs, red pepper flakes, and fennel. Cook the onions and garlic for about 5 minutes until they are translucent.
While the onions are cooking, place the scraped zucchini filling in a cheese cloth or a thin, clean tea towel and squeeze out the excess liquid, then add it to the pan with the onions and sauté for 3-4 more minutes.
Add 2 cups of cooked lentils (or other vegan protein of choice) and 1 cup of pizza sauce. Stir well and simmer on low for about 5 minutes.
Stuff and bake the zucchini boats
Once the zucchini has baked for 15 minutes, take them out of the oven and fill them with the lentil mixture. Top with vegan pizza cheese sauce or vegan mozzarella and place back into the 425° F (218° C) oven for 20 more minutes.
Notes
Use a sharp paring knife to cut an outline around the zucchini where you want to scoop out the middle.
Be sure to leave about 1/4 inch of the zucchini for the boat. You don't want it to get too thin, or it will fall apart.
If the zucchini has big seeds, you can discard them. Don't use the seeds in your filling
If cooking your own lentils, boil 1 1/4 cups of green lentils in salted water for 18 minutes, then drain and rinse.