In a large heavy saucepan heat oil over medium-high heat. Add farro; cook and stir 5 to 6 minutes or until toasted and has a nutty aroma. Stir in the water, onion, and salt. Bring to boiling; reduce heat. Simmer, covered, 30 minutes or just until farro is tender.
Remove 2 tsp. zest and squeeze 3 Tbsp. juice from lemon. Stir lemon zest, cauliflower, garlic, turmeric, and pepper into farro mixture.
Cook, covered, over medium-high heat 4 minutes. Cook, uncovered, 4 minutes more or until cauliflower is tender and liquid is absorbed, stirring occasionally. Stir in lemon juice and thyme.