Heat a large sauté pan, lightly coated with evoo, over medium-high heat. Sear lemon slices for just a minute until they begin to brown.
Add green beans, garlic, salt, and pepper and sauté until beans begin to cook through, about 3 to 5 minutes.
Add zest, juice, sumac, and parsley. Continue cooking for another 5 minutes until beans are tender but not mushy.
Transfer beans to platter and garnish with additional sumac.
