Place the Fine bulgur (No. 1) in a bowl and cover with just-boiled water; let soak until tender (about 10–15 minutes), then drain thoroughly and gently squeeze out any excess moisture.
While the bulgur soaks, very finely chop the Flat-leaf parsley (stems removed or mostly trimmed) and the Mint; the herbs should be almost chiffonaded so the salad feels light and green.
Core and dice the Tomatoes into small pieces and thinly slice the Scallions (spring onions); if your tomatoes are very juicy, scoop out some seeds to prevent the salad from getting watery.
Transfer the drained bulgur to a large bowl and fold in the chopped parsley, mint, tomatoes and scallions until evenly distributed.
Pour in the Lemon juice and Extra-virgin olive oil and toss to coat; season with Sea salt and freshly ground Black pepper to taste, adjusting lemon and oil until the balance is bright and fresh.
Taste and adjust seasoning—tabbouleh should be lively with lemon and fairly herb-forward—then let the salad rest in the refrigerator for at least 20–30 minutes so the flavors meld.
When ready to serve, wash and separate the leaves of the Romaine lettuce and use them as crisp cups or place the tabbouleh in a bowl with lettuce on the side for scooping.
Serve chilled or at cool room temperature; this keeps well for a day and often tastes even better after the flavors have had time to marry.
