Preheat oven to 400°F.
To make Walnut Feta, add walnuts, nutritional yeast, and sea salt to a food processor. Process until the walnuts become grainy, making sure to stop and scrape down the sides when necessary. Add olive oil, and continue to process until small clumps form. Do not over process, it will eventually become a paste-like texture.
Using a sharp knife, slice the top of the tomatoes off, making sure to include the stem. Take a large spoon and scoop out the insides of the tomato, leaving about 1/2"-3/4" thickness around the outside.
Preheat a cast iron skillet over medium heat. Add olive oil, shallots, and garlic. When it begins to sizzle, add the salt. Saute until shallots begin to lightly brown. Add mushrooms, artichokes, and zucchini, continually stirring mixture so that no sticking occurs. Lightly salt, and saute until mushrooms release their moisture and the vegetables are tender. Remove from heat and add the nutritional yeast and cumin. Mix thoroughly until vegetables are evenly coated.
Fill tomatoes to the brim with the vegetable mixture, and then sprinkle on the walnut feta. Place in a large casserole dish and bake in preheated oven for about 15 minutes, or until walnut feta is lightly browned. If left in the oven for too long, tomatoes will begin to split down the sides.
Remove from oven and serve immediately.