In a pot of boiling salted water, cook the farro until done, about 10 minutes. Drain. Transfer to large bowl.
Meanwhile, in a medium sauté pan on medium high heat, caramelize the onion and fennel in a few Tbsps of olive oil, about 5 minutes. Add to the farro. Toss in the olive oil, vinegar, tomatoes, and basil. Season to taste with salt and pepper.