Saute the onion in a small pan over medium high heat. Once the onions are cooked, add the can of black beans and the can of tomatoes. Cook until the mixture is heated through.

Spread the black bean and tomato mixture onto one side of 4 tortilla shells. Sprinkle about 2 tablespoons of shredded cheese on top of each. Cover with another tortilla shell. Heat through using a skillet or panini press–about 2-3 minutes per side. Cut each tortilla into 4 pieces. Consider topping with lettuce and tomato and using plain greek yogurt in place of sour cream. Serves 4.

Each serving is approximately 400 calories.

A great recipe calorie calculator can be found here: http://recipes.sparkpeople.com/recipe-calculator.asp