Cook the pasta in a large pot of salted boiling water (7-9 minutes). Once the pasta is al dente, save ½ cup of pasta water and drain the rest.
Meanwhile, add vegan butter to a large saucepan over medium heat. Add the pressed garlic to the pan when the butter has melted and let it cook for 1 minute.
Gradually sprinkle the flour into the pan. Whisk it as it cooks for 2 minutes. It will become thick and smooth.
A little at a time, pour the plant milk into the pan as you stir. Let it cook for 10 minutes, stirring occasionally. The sauce will thicken during this time.
Stir in the nutritional yeast, seasoning, lemon juice, and pasta water. Let it cook for 2 minutes.
Gently combine the cooked pasta with the alfredo sauce until it's fully coated. Garnish with optional pepper, cayenne, and fresh parsley.