Vegetable Ravioli

Process flour, eggs, ½ teaspoon salt and 3 teaspoons of water to a smooth dough, form into a ball, wrap in foil and let rest for half an hour. Trim, rinse and finely chop vegetables. Peel onion and finely chop. Cut scallions into thin rings. Heat oil in a pan,  sauté onion, then cook remaining vegetables. Season with lemon juice, salt and pepper. Allow vegetables to cool slightly, then mix with egg yolk and Parmesan. Roll out the pasta dough very thin on a lightly floured surface and distribute the vegetable mixture in 20 hazelnut-size servings at a distance of 4 cm (approximately 1 1/2 inches) apart on the dough surface. Moisten the gaps with water and fold over the second half of pasta. Press well around the filling and let rest for 2 minutes. Cut with a wheel into 20 small squares and cook for 5 minutes in boiling salted water.