Sauté the onion and garlic in the olive oil until onion is translucent, about 5 minutes.
Stir in the mushrooms and cook about 10 minutes.
Combine the mushrooms, walnuts, lentils, breadcrumbs, garlic powder and onion powder in a food processor and pulse until smooth. Season to taste with salt and pepper.
Form into small golf-ball sized meatballs.
Heat olive oil in a pan. Place the meatballs inside and cook, turning often until golden brown and crispy all around.
For the sauce, the onion and garlic in 1 tablespoon of olive oil. Add the tomatoes, oregano, salt, and balsamic vinegar. Simmer for 15 minutes. Season with additional salt and pepper to taste.
To serve, cook 8-16 ounces of spaghetti, spiralize 2-4 zucchinis, or use a combination of both. Top with the sauce and "meatballs".