Bring a large pot of well-salted water to a boil over high heat. Add the escarole and cook until the stem pieces start to soften, about 2 minutes (the water needn’t return to a boil). Drain, run under cold water to cool, and drain again.
In a 12-inch skillet, heat the olive oil and garlic over medium heat, stirring occasionally, until the garlic browns slightly, 2 to 3 minutes. Remove the garlic with tongs and discard. Add the pine nuts, raisins, capers, and pepper flakes and cook, stirring, until the pine nuts are golden and the raisins puff, about 1 minute. Add the escarole, increase the heat to medium high, and cook, tossing often, until heated through and tender, 3 to 4 minutes. Sprinkle with the lemon juice and season to taste with salt.