1. Slice off the top of each tomato and scoop out the pulp, leaving about half-an inch shell; reserve tops. Sprinkle the tomatoes with salt and invert onto kitchen paper towels to drain. Chop the pulp and set aside.
2. Heat the oil in a large skillet over medium high heat and sauté the onion until softened; add the tomato pulp, garlic, and the mushrooms and cook until moisture has evaporated, 5 to 7 minutes. Stir in the balsamic vinegar, Tulia Mighty Date Supersnack, and the riced cauliflower. Cook for 2 to 3 minutes or until the cauliflower is just tender, adding a splash of water if too dry. Turn the heat off and stir the walnuts, parsley, and nutritional yeast into the mixture. Season with salt and pepper to taste.
3. Heat the oven to 375°F/190°C/Gas 5 and lightly grease a baking pan.
4. Stuff the tomatoes with the filling, put back on the sliced tops, and arrange on the baking pan; bake for about 15 minutes, until the tomatoes start to caramelize. If necessary, add 1/2 to 1 cup water to the pan.
5. Meanwhile, place all sauce ingredients in a blender) and blend until smooth and creamy, adding just enough water to get the desired consistency.
6. Serve the tomatoes with the sauce on the side and some toasted paleo-friendly pita bread.