Bring a large pot of salted water to a boil and cook the pasta until just shy of al dente, about 1-2 minutes less than package instructions. Drain and set aside.
In a skillet, heat olive oil over medium heat. Add minced garlic and chopped onion, sautéing until fragrant and translucent, about 2 minutes. The aroma should turn sweet and the garlic golden at the edges.
Add the mixed vegetables to the skillet and cook, stirring occasionally, until they are tender and slightly caramelized, about 5 minutes. They should release some moisture and develop a lovely aroma.
In a large mixing bowl, combine the cooked pasta, sautéed vegetables, tomato sauce, and nutritional yeast. Mix thoroughly with a spatula or spoon until everything is evenly coated and combined.
Transfer the mixture into a greased baking dish, spreading it out evenly. Sprinkle a little extra nutritional yeast or vegan cheese on top for a golden, cheesy crust.
Bake in a preheated oven at 180°C (350°F) for 20-25 minutes, until bubbling around the edges and the top is golden brown. The aroma of roasted garlic and baked tomato will fill your kitchen as it cooks.
Remove from the oven and let rest for about 5 minutes. This allows the dish to set slightly, making it easier to serve and preventing it from being too runny.
Serve hot, garnished with fresh herbs if desired. Enjoy the comforting, cheesy aroma and hearty texture of this cozy vegan pasta bake.