Puree the purslane, sunflower seeds and garlic with the lemon zest and juice. Add the cheese, mix in the oil, season with salt.
Cook the spaghetti in boiling salted water until just al dente. Set aside approx. 100 ml of cooking water, drain the spaghetti. Return the spaghetti to the pan, mix in the reserved cooking water and pesto, plate up. Top with the purslane, cheese and sunflower seeds.