Soak cashews in filtered water for at least 30 minutes or up to 4 hours and drain. Note that if you have a high powered blender, 30 minutes is sufficient, but that longer periods may be required for less powerful blenders.
Add cashews, soy milk, garlic and onion powder to blender and blend to produce a smooth creamy consistency. Set aside.
Bring a large pot of water to a boil to cook pasta.
Heat a large pan on medium heat and melt vegan butter. Add chopped onion and garlic, salt and pepper and sauté until translucent, about 10 minutes, stirring periodically to prevent sticking or burning.
Add the nutritional yeast to the pan and stir to combine, cooking for a minute or so. Add lemon juice and stir. Turn heat to medium/low.
Add pasta to boiling water and cook until al dente.
While pasta is cooking, pour in cashew cream and stir to combine. Then add vegetable broth and continue to stir to a smooth consistency. Add peas and continue to heat for approximately 10 minutes until sauce starts to thicken. It should remain runny enough so that when stirred, the path of the spoon does not show noticeably. If the sauce remains over the heat, you may need to add a little more broth to maintain a slightly runny consistence. This sauce will always appear thicker once combined with the pasta. Feel free to add a little more vegetable broth or soy milk if you need to thin the sauce.
Once pasta is cooked, drain and rinse in a colander. You can add the pasta directly to the pan with the sauce and stir to combine. Serve family style. Or, if you are not eating all the pasta at one time just add sauce to individual bowls of pasta so that you can store the pasta and sauce separately and have as leftovers.