Rinse quinoa in fine mesh strainer until water runs clear
In medium saucepan, combine quinoa with 200ml water and bring to boil
Reduce heat to low, cover, and simmer for 15 minutes until water is absorbed
Remove from heat and let stand 5 minutes, then fluff with fork and cool completely
While quinoa cooks, prepare vegetables: dice tomatoes, cucumber, and bell pepper into 1cm pieces
Finely dice the red onion and slice spring onions
Chop lettuce into bite-sized pieces
For dressing: whisk together tahini, olive oil, lemon juice, minced garlic, cumin, oregano, salt, and pepper in small bowl
Gradually add water until dressing reaches pourable consistency
In large mixing bowl, combine cooled quinoa, white beans, and all prepared vegetables
Pour dressing over salad and toss gently to combine
Let salad rest for 10 minutes to allow flavors to meld
Taste and adjust seasoning if needed