Simmer sugar and water in a large heavy saucepan, stirring, until sugar is dissolved. Gently stir in figs, zest, and lemon juice and simmer, uncovered, stirring occasionally, until thick and syrupy, 1 3/4 to 2 hours. Gently stir in sesame seeds.
Jam keeps, covered and chilled, 1 month.Toast seeds in a dry heavy skillet over moderate heat, stirring until fragrant and a shade or two darker. Or, toast in a shallow baking pan in a 350°F oven, 5 to 10 minutes.
