Peel the cucumber and slice it into fine slices, place in a sieve, add plenty of salt and leave to stand for about 30 minutes, then squeeze out a little and place in a salad bowl.
Cut the onion into fine cubes.
Mix the oil, vinegar, salt, pepper and sugar to taste.
Add the dressing, onions and sunflower seeds to the cucumber slices and mix, let the salad steep a little.