Preheat your oven to 200°C (390°F). Halve the ripe tomatoes and spread them out evenly on a baking sheet. Drizzle with 1 tablespoon of olive oil and sprinkle with a pinch of salt. Roast for 25-30 minutes until the skins blister and the tomatoes are soft and fragrant.
While the tomatoes roast, cook the pasta in a large pot of salted boiling water according to package instructions until al dente, about 8-10 minutes. Drain, reserving about a cup of the pasta water, and set aside.
In a blender, combine the roasted tomatoes, soaked cashews, minced garlic, lemon juice, and 2 tablespoons of olive oil. Blend until the mixture is completely smooth and creamy, scraping down the sides as needed.
Pour the sauce into a large skillet over medium heat. Let it simmer gently for about 5 minutes, stirring occasionally, until slightly thickened and fragrant. Taste and season with salt and pepper as needed.
Add the cooked pasta directly into the skillet with the sauce. Toss gently to coat the noodles evenly, adding reserved pasta water a little at a time if the sauce needs loosening. Cook for another minute until well combined.
Finish by stirring in chopped fresh basil and a drizzle of olive oil. Serve immediately, garnished with extra basil if desired, for a bright and velvety pasta dish.