Cook the pasta. Bring a large pot of water to a boil over high heat. Season with 2 tablespoons of salt. Add the spaghetti and stir to make sure the pasta doesn’t clump together. Boil until al dente, 6 to 7 minutes. Reserve 1 cup pasta cooking water and drain noodles. Rinse the chickpea noodles under cold water until completely cooled. Put aside.
Prepare the sauce. Meanwhile, heat a large saucepan over medium-high heat. Add 2 tablespoons of olive oil and toss to coat. Add garlic, red pepper flakes and onion powder, if using. Sauté, stirring, until garlic is fragrant, 30 seconds to 1 minute. Do not brown. Add cherry tomatoes and dried herbs, if using, and season with salt and pepper. Continue cooking until the tomatoes begin to break down, 4 to 5 minutes. Add tomato paste and harissa paste and cook for 3 more minutes. Taste the sauce and season with salt, pepper and additional harissa paste, if desired. (Pasta sauce can be made up to 3 days ahead. Store, covered, in the refrigerator before reheating in a skillet.)
To serve. Add the pasta to the sauce, along with 1-2 tablespoons pasta water to thin, if needed. The sauce should be thick and concentrated, but just loose enough to coat the noodles easily. Cook 1 minute more, stirring to combine. Add chopped basil, gently fold to combine and divide among serving plates. Serve immediately, garnishing each serving with a drizzle of olive oil and additional basil.