In a small bowl, combine mayonnaise, lemon juice, and cumin; mix well and
spread over 1 side of 4 slices of bread. Top each with 2 slices of Cheddar cheese,
1 sliced tomatillo, 1 tablespoon chiles and remaining 4 slices of bread.
Melt the butter in a large skillet or griddle over low heat.
Cook the sandwiches, covered for 3 to 4 minutes each side, until golden
and the cheese is melted.