Light the grill or heat the broiler. In a small glass or stainless-steel bowl, combine the beans, scallions, lemon juice, cumin, and 1/4 teaspoon of the salt.
Rub the chicken breasts with the chili powder, pepper, and the remaining 1/4 teaspoon salt. Cook the chicken over moderate heat for 5 minutes. Turn and cook until brown and just done, 4 to 5 minutes longer. Remove, let the chicken rest for a few minutes, and then slice.
Heat the oven to 350°. Put one quarter of the cheese in a line near one edge of each tortilla. Top the cheese with one quarter of the black-bean salsa and then with one quarter of the chicken slices. Roll up the burritos and wrap each one in foil. Bake them until the cheese melts, about 15 minutes.
Menu Suggestions: Embellish your burritos with sour cream or salsa, if you like. Sliced tomatoes or rice would make good side dishes.
Do-Ahead Tip: You can assemble the burritos ahead of time and bake them just before serving. If theyve been in the refrigerator, add about five minutes to the baking time.
Wine Recommendation: With the heat from the cheese, stay away from any serious, high-alcohol, low-acid wines. Try a white from a cooler growing area such as a riesling from the Finger Lakes region of New York or any white from the Alto Adige region of Italy. A cold beer is a great alternative.