Market Sandwich

1/2 cup white vinegar

1 cup thinly sliced red onion

1 cup canned black beans, rinsed and drained

1/2 teaspoon ground cumin

1/4 cup fat-free mayonnaise

1 teaspoon finely chopped canned chipotle chile with sauce

1 tablespoon fresh lime juice

8 slices whole-grain bread

2⁄3 cup crumbled reduced-fat feta

1 medium avocado, thinly sliced

2 tablespoons fresh cilantro, chopped

1 tomato, cut into 8 slices

Boil 1 cup water with vinegar in a small stainless steel saucepan. Add onion; turn off heat; let sit 30 minutes; drain. Puree beans and cumin in a blender. Mix mayonnaise, chipotle and lime juice in a bowl; spread on 4 slices of bread. Top remaining slices with bean puree, onion, cheese, avocado, cilantro and tomato. Close sandwiches; serve.