Preheat your oven to 200°C (390°F). Wrap the whole head of garlic in foil with a tablespoon of olive oil, then roast for 30-40 minutes until soft, golden, and fragrant.
While the garlic roasts, chop your ripe tomatoes or open a can of crushed tomatoes. Set aside.
Cook your pasta in a large pot of salted boiling water until al dente, about 8-10 minutes. Drain and set aside, reserving some pasta water.
Once the garlic is roasted and cool enough to handle, squeeze out the soft, caramelized cloves into a blender.
Add the chopped tomatoes, soaked cashews, lemon juice, and a splash of water to the blender. Blend until the sauce is completely smooth and creamy, with a velvety texture.
Pour the sauce into a sauté pan and simmer gently over medium-low heat for about 10 minutes, stirring occasionally. It will thicken slightly and develop a fragrant, smoky aroma from the roasted garlic.
Taste the sauce and add salt and red pepper flakes as desired to balance flavors and add a bit of heat. If it gets too thick, stir in a little reserved pasta water to loosen it.
Add the cooked pasta to the sauce, tossing gently to coat each strand evenly. Warm through for 2-3 minutes until the pasta is well coated and heated.
Turn off the heat and let the pasta sit for a minute to allow the flavors to meld. Then, stir in the chopped fresh basil for a burst of herbal aroma.
Squeeze a little extra lemon juice over the pasta if desired, drizzle with a splash of olive oil, and serve hot, garnished with more basil if you like.