1. Light the grill. In a small bowl, combine the garlic, grapefruit zest, grapefruit juice, oil, honey, salt, and pepper.
2. Grill the chicken breasts over moderately high heat, brushing frequently with the glaze, for 8 minutes. Turn and cook, brushing with more glaze, until the chicken is just done, 10 to 12 minutes longer. Remove.
3. In a small stainless-steel saucepan, bring the remaining glaze to a boil. Boil for about 1 minute, remove from the heat, and pour over the grilled chicken.
Menu Suggestions: Since the chicken breasts don't have a lot of sauce, serve a juicy vegetable such as grilled or sautéed summer squash or zucchini alongside.
Variation: Grilled Chicken Breasts with Citrus Glaze: Use a combination of citrus juices, such as orange, lemon, or lime, instead of all or part of the grapefruit juice.
Wine Recommendation: The crisp acidity, effervescence, and moderate alcohol level of a brut Champagne from France or a sparkling wine from California will be perfect with the smokey taste here and with the high acidity of the grapefruit juice.