Bring a large pot of salted water to a boil. Add the green beans and cook until tender, about 5 minutes. Drain well.
Heat the oil in a large skillet over medium heat. Add the onions and garlic and cook, stirring occasionally, until soft, about 5 minutes. Add the smoked paprika and cook for 30 seconds, stirring. Add the green beans and more oil if needed; cook, stirring, until the beans are well coated, about 1 minute. Stir in the lemon juice and season with salt and pepper.