Place water and farro in a medium saucepan to presoak for 5 to 10 minutes.
Prepare the other ingredients: cut onion in half and thinly slice into quarter-moons, thinly slice garlic cloves, and halve or quarter tomatoes.
Add salt, pepper flakes, and 1 tablespoon olive oil to the pan.
Set a timer for 30 minutes, bring the uncovered pan to a boil, then reduce to a gentle simmer, stirring occasionally.
When the timer rings, the farro should be perfectly cooked and the cooking water should be almost completely absorbed.
If needed, cook for an additional 5 minutes until farro is more tender.
Transfer to a wide serving bowl, drizzle with additional olive oil, scatter with basil and parmesan, and eat immediately.
