Fold a piece of foil into a square and turn the edges upwards. Heat a gas grill (or grill pan) to medium or light a charcoal fire and let it burn until medium hot. Place the limes, cut side down, on the piece of foil and grill for 3-4 minutes. Flip and grill for 3-4 minutes more. Remove from grill and allow to cool.
Using a Mexican lime squeezer, juice the limes into a glass measuring cup (and add any juice leftover in your foil tray), yielding about 1/3 of a cup. Pour the lime juice into a blender jar and add the cilantro, chiles, honey, and 1 teaspoon salt. Blend, adding oil in a thin stream until the mixture is smooth.