In a large, deep skillet, heat the oil. Add the cumin and cook over moderately high heat until slightly darkened, 10 seconds. Add the jalapeños and ginger and cook, stirring, until fragrant, 1 minute. Stir in the chard leaves and stems with the water that clings to the leaves and a pinch of salt. Cover and cook over low heat, stirring, until the chard is tender, 12 minutes. Uncover and cook over high heat until most of the liquid has evaporated, 2 minutes. Add the lemon juice, season the chard with salt and serve.