How to Make It
Heat the oven to 350°. In a medium saucepan, combine the lentils, onion, the 2 3/4 cups water, the oil, 1 teaspoon of the salt, and the bay leaf. Bring to a boil; simmer, partially covered, for 15 minutes. Stir in the bulgar and continue cooking, partially covered, stirring occasionally, until the lentils and bulgar are just done, about 12 more minutes. Remove from the heat, stir in the Tabasco sauce, and let sit, partially covered, for 5 minutes. Remove the onion and the bay leaf.
Meanwhile, in a medium glass or stainless-steel bowl, whisk together the tahini, the remaining 6 tablespoons water, the garlic, the lemon juice, the remaining 1 1/2 teaspoons salt, and the yogurt.
Wrap the pitas in aluminum foil and warm them in the oven, about 10 minutes.
Cut the top third off of each pita. Spoon 1/4 cup of the lentil mixture into each pita. Divide half the chicken and tomatoes among the pitas and drizzle each with 1 tablespoon of the sauce. Top with half the lettuce. Repeat. Serve with the remaining sauce.