Cut the ends off of the zucchinis and then cut them in half, lengthwise. Use a spoon to scoop out the inside pulp of the zucchinis and finely chop the pulp.
Set the zucchini boats on a rimmed baking sheet lined with parchment paper or a silicone baking mat. Set aside.
In a large skillet, heat the avocado oil over medium heat. Add the onions, mushrooms, zucchini pulp, and season with salt and pepper. Cook until softened and the mushrooms and zucchini pulp release their liquid and cook down, about 7 minutes.
Add the cooked lentils, tomato sauce, and taco seasoning and stir to combine well. Allow this mixture to gently simmer for 10 minutes.
Transfer the lentil taco mixture evenly to the inside of the zucchini boats. Cook in the preheated over for 20-25 minutes, until the zucchini is tender.
Serve with optional toppings. Enjoy!
*I use canned lentils that I drain the liquid from for this recipe.