1. Combine olive oil, chopped onion, minced garlic, cumin seed, black beans, salt, mayonnaise, and minced chipotle in adobo, in medium bowl; set aside.
2. Heat oil in skillet over medium-high heat. Add onion; cook 2 minutes. Stir in garlic and cumin; cook, stirring, 30 seconds. Add beans and salt; cook, stirring, until heated through. Lightly mash; cover and set aside.
3. Combine mayonnaise and chipotle in cup. Cut each pita in half crosswise. Spread mayonnaise on one side of pita halves. Spread bean mixture over mayonnaise; top with salsa and lettuce. Makes 4 servings.