Bring a large pot of water to a boil. Add pasta and cook according to package directions. Drain into a colander, then return pasta to the pot. Toss with olive oil.

While pasta cooks, place cashews, ¾ cups of milk, lemon juice, miso paste and garlic into a food processor or blender. Blend until completely smooth, thinning with up to an additional ½ cup of milk, and stopping to scrape down sides of bowl or pitcher as needed.

Pour cashew mixture over pasta. Add tomatoes, basil and capers, then season with salt and pepper to taste. Toss until ingredients are mixed and coated with sauce.

Divide onto plates, sprinkle with red pepper flakes, if using, and serve.