In a large pot, add water and bring it to a boil. Add fettuccine noodles and cook according to instructions for al dente on package. Once cooked pour into a drainer and set aside.
In a large skillet or deep fry pan, heat the vegan butter over medium heat. Add the minced garlic and cook for 1 minute or so, until the garlic is aromatic and cooked but not browned.
Add the gluten free flour. Stir until well mixed.
Add the soy milk or cream as well as the lemon juice, nutritional yeast, vegan parmesan and the seasonings. Stir well for 1 minute to mix and to prevent curdling.
Reduce heat to medium low and cook sauce, stirring constantly, about 5-8 minutes. You will know its done when it becomes creamy, not runny. If too thick, add some of the pasta water until it's a creamy consistency. Turn off heat but keep pan on the burner.
Add the cooked fettini noodles and gently stir them until they are well coated with sauce. Remove pan from heat.
Serve immediately. Garnish with chopped parsley.