Cook the pasta according to package instructions until al dente. Drain and set aside.
In a large skillet, heat the olive oil over medium heat. Add the sliced onions and cook, stirring occasionally, for about 15-20 minutes until they are caramelized and golden brown.
Add the minced garlic, dried thyme, salt, and black pepper to the skillet. Cook for an additional 2 minutes until fragrant.
Pour in the vegetable broth and almond milk, stirring to combine. Bring the mixture to a simmer.
Stir in the nutritional yeast and soy sauce. Then, add the cornstarch mixture to thicken the sauce, stirring continuously until the sauce is creamy and coats the back of a spoon.
Add the cooked pasta to the skillet, tossing to coat the pasta evenly with the sauce. Cook for an additional 2-3 minutes until heated through.
Remove from heat and stir in the lemon juice. Serve warm, garnished with fresh parsley.