Bring a large pot of salted water to a boil. Add your pasta and cook al dente according to package instructions. Reserve about ½ cup of pasta water before draining.
Heat a large skillet over medium heat with olive oil. Once hot, cook the onion and garlic until the garlic is translucent, about 3-4 minutes. Add the red pepper flakes and cook for an additional minute, then add tomato paste. Cook until the sauce has darkened, 2-3 minutes.
In a blender, combine the roasted red peppers, sauteed onion and garlic mixture, oat milk, and nutritional yeast. Season to taste with kosher salt and freshly ground black pepper. Blend until smooth.
Pour half the sauce (1.5 cups) back into the skillet and warm over low heat. Let the remainder of sauce cool to room temperature, then store it in the fridge or freeze for later use.
Stir in the butter until melted. Add the cooked pasta and toss to coat, adding a few tablespoons of the reserved pasta water as needed for a silky texture.
Top with torn fresh basil leaves. Enjoy!