In a large bowl, mix together half the scallions, the garlic, coriander, cumin, cayenne and turmeric. Add the shrimp and stir to coat. Cover with plastic wrap and refrigerate for 30 minutes.
In a large skillet, heat the oil over medium-high heat. Add the shrimp and cook, stirring constantly and seasoning with the salt, until nearly opaque, about 2 minutes. Add the lemon juice and continue frying until the shrimp are cooked through, about 1 minute more. Top with the remaining scallions.