Preheat oven to 425F.
Cut the cauliflower in to large bite size pieces.
Toss the cauliflower with olive oil, salt, and pepper. Spread evenly on a parchment lined baking tray. Bake for 30 minutes, tossing halfway.
Boil water and cook pasta of choice according to package. Reserve ½ cup of pasta water.
Heat a pan on medium-high heat. Add the olive oil, the diced yellow onion, and a pinch of salt. Cook for 7 minutes or until the onions are soft and starting to brown.
Add in the garlic and cook for another 2 minutes.
Add half of the roasted cauliflower to a blender along with the cooked onions and garlic, miso paste, lemon juice, plant milk, water, black pepper, and salt. Blend until smooth and creamy. Taste and season with more salt, if desired.
Pour the cauliflower alfredo sauce in the pot with the pasta and toss until evenly combined. Add in the reserved pasta water to thin out the sauce to the perfect texture. You may not need the entire ½ cup.
Divide the pasta on to serving plates and top with the remaining roasted cauliflower and fresh basil and parsley. Enjoy!