Place raisins in a medium bowl and pour vinegar over (it should cover raisins). Let sit, stirring occasionally, 10 minutes for raisins to soften. Meanwhile, combine oil and almonds in a small skillet and set over medium heat. Cook, stirring occasionally, until flesh is golden brown, about 5 minutes. Transfer to a small bowl and let cool. Mix raisins, onion, lemon zest, and red pepper flakes into almonds; season with salt. Let sit 10 minutes. Toss in parsley just before serving. Agrodolce (without lemon zest and parsley) can be made 3 days ahead. Cover and chill. Bring to room temperature before using.