Rinse the quinoa under running water and place it in a pan with plenty of water. Bring to a boil and cook the quinoa for twelve minutes until tender. Drain and let the grains cool completely so the other ingredients won't become warm later.
Rinse the fresh parsley and mint, shake them dry, and finely chop both herbs with a sharp knife. Then cut the tomato and half cucumber into small, uniform cubes.
Take a large bowl and add the cooled quinoa to it. Add the tomato and cucumber cubes together with the finely chopped parsley and mint. Pour in the olive oil and juice of the half lemon, toss everything together well, and season the mixture with pepper.
Divide the tabbouleh over the plates or spoon it into a serving bowl. Crumble the sheep feta with your fingers and sprinkle it over the salad, then serve the dish immediately.