Combine the scallops with the turmeric in a medium-size bowl. Refrigerate, covered, for 30 minutes or as long as overnight, to allow the flavor to permeate the thick muscle (since there is nothing acidic to break down the mollusk's texture, it's fine to marinate them overnight).
Pour the peanuts into the bowl of a food processor and pulse until they have the consistency of coarse breadcrumbs.
Heat the oil in a large skillet over medium heat. Add the scallops, marinade and all (there won't be much at the bottom of the bowl), arranging them in a single layer. Sear the scallops' two broad sides until light brown, 3 to 5 minutes per side. Transfer them to a plate.
Add the garlic to the same skillet and stir-fry until it is light brown, about 1 minute. Pile in the spinach leaves, cover the skillet, and cook until the spinach is wilted, 5 to 8 minutes. (As the steam rises from within, the leaves will sweat and release their liquid, which will deglaze the pan and build yet another layer of flavor.) Stir in the masala and salt.
Add the scallops (including any liquid pooled in the plate), and cover them with a blanket of the wilted greens. Cover and cook, without stirring, until the scallops are firm to the touch but not rubbery, 3 to 5 minutes.
Transfer the scallops to a serving platter. Add the peanuts to the spinach in the skillet, and stir to combine. Simmer, uncovered, stirring occasionally, to allow the nuts to absorb the excess liquid and thicken the sauce, 2 to 4 minutes.
Spoon the spinach-peanut mixture over the scallops, and serve.