- In a large pot, bring 4 quarts water to a boil over high heat.
- Meanwhile, in a mixing bowl, mash the avocado.
- Stir in the lime or lemon juice, onion, tomato, chopped basil, and salt and pepper to taste.
- Set aside.
- When the water boils, stir in 1 tablespoon salt, add the pasta, and cook until tender but still firm to the bite.
- Drain and transfer to a preheated bowl.
- Quickly stir in the reserved avocado mixture.
- Garnish with basil sprigs and serve immediately.
- Pass the cheese at the table.