Wipe out the skillet and then heat the remaining 1 Tbs. oil over medium-high heat. Add about two-thirds of the scallions and cook, stirring constantly, until softened, about 30 seconds. Add the spinach, cilantro, and 1/4 tsp. salt and cook, tossing constantly with tongs, until just barely wilted, about 2 minutes. Remove the skillet from the heat, drizzle the spinach mixture with the sesame oil, and toss to combine well.