Steam the beans in a medium saucepan by adding ¼ cup water to a covered saucepan over medium-high heat.

Drain but reserve the cooking water.

Mix the tahini, garlic, lemon zest and juice, and salt and pepper to taste. Use the reserved cooking water to thin the sauce as desired.

Toss the green beans with the sauce and serve warm or at room temperature.

Garnish with the sesame seeds.