Roasting red peppers over a flame: Roast red pepper over a flame until charred on all sides, repeat with second pepper. When cool, remove skin and seeds. Roasting red peppers in an oven: Drizzle olive oil in a pan. Slice red peppers in half, remove seeds, and place with skin facing up. Drizzle a little more olive oil on top. Add salt and pepper. Roast @ 450° for about 25 minutes, or until charred. Remove skin after peppers have cooled.
Cook pasta according to directions, but slightly al dente. Save a little of the pasta water.
Heat olive oil in a skillet and cook chopped onion until translucent. Add minced garlic. Cook for a minute longer.
Put onion, garlic, and roasted red pepper in a food processor. Add unsweetened almond milk, vegetable broth, and nutritional yeast, and blend until smooth. Add salt and pepper and blend.
Pour sauce and pasta with some of the pasta water back in skillet and cook for a few minutes until heated.