Heat 2 Tbsp. extra-virgin olive oil in a medium heavy-bottomed saucepan over medium. Add lemon zest and 8 scallions, thinly sliced, and cook, stirring often, until scallions are bright green and beginning to soften, about 2 minutes. Add 1 cup basmati rice, rinsed, drained well, 1½ tsp. Diamond Crystal or 1 tsp. Morton kosher salt, and half of 1 bunch dill, tough stems trimmed, finely chopped, and cook, stirring, until rice is coated in oil, about 30 seconds. Pour in 1¼ cups plus 2 Tbsp. water and bring to a boil. Reduce heat to low, cover pan, and simmer until rice is nearly tender and water is absorbed, 13–15 minutes.