01 - Preheat oven to 425°F.
02 - On a baking sheet, toss cauliflower florets and red onion with 2 tablespoons olive oil, salt, and pepper. Spread in a single layer. Roast for 25–30 minutes, stirring halfway, until golden and tender.
03 - Rinse barley under cold water. In a saucepan, combine barley, water, and 1/2 teaspoon salt. Bring to a boil, reduce heat to low, cover, and simmer for 25–30 minutes until barley is tender but chewy. Drain excess water if needed.
04 - In a bowl, whisk together tahini, lemon juice, olive oil, minced garlic, and warm water until smooth. Season with salt and pepper. Add more water for a thinner consistency if desired.
05 - In a large bowl, combine warm barley, roasted cauliflower, and onion. Drizzle with dressing and toss to coat.
06 - Stir in parsley and half the pine nuts (or almonds). Taste and adjust seasoning if needed.
07 - Serve warm, garnished with remaining nuts and feta cheese, if using.