Preheat broiler and line broiling pan with a very lightly oiled sheet of foil. Trim and halve figs. Stir together yogurt, sour cream, zest and 1 1/2 tablespoons sugar until smooth. Spread remaining 1 1/2 tablespoons sugar on a small plate. Dip cut sides of figs in sugar, cut sides up, on broiling pan (for best results, arrange figs so they will be directly under the flame). Broil 2 inches from flame until bubbling and caramelized, about 3 minutes.