Cut top 1/2 inch off garlic; wrap loosely in foil. Bake in a 350° oven until soft when pressed, about 45 minutes. Let cool, then squeeze garlic from skins into a 3- to 4-quart pan (discard skins). Add chiles, tamarind concentrate, cilantro, 1 cup water, honey, lime juice, pepper, and salt to pan. Bring to a boil over medium-high heat, stirring often; remove from heat and let stand 10 minutes. Pour into a blender or food processor and whirl until smooth.