Pasta Primavera - Lidia

Ingredients

• 6 quarts water for boiling plus a bowl of ice water
• 1/3 cup extra-virgin olive oil
• 1/2 cup onion, sliced
• 2 garlic cloves, crushed
• 1 (28-ounce) can San Marzano or other Italian plum tomatoes, with their juices, crushed by hand or 1 1/2 cups of ripe cherry tomatoes, cut in half
• 1 pound spaghetti
• 1/2 teaspoon salt
• 4 basil leaves, shredded
• 1/2 cup Grana Padano cheese, grated