Rinse the canned chickpeas thoroughly under cold running water and let them drain well in a colander. Let the roasted red bell pepper also drain and cut the flesh into thin strips. Make the dressing in a small bowl by vigorously mixing a splash of olive oil and some lemon juice together.
Heat a small pan over the stove without adding oil or butter. Toast the sunflower seeds for a few minutes in the dry, hot pan. Shake the pan regularly to prevent burning. Remove the seeds from the pan immediately once they turn light golden and begin to smell.
Take a large mixing bowl and add the already cooked quinoa, the drained chickpeas, the strips of roasted bell pepper and a handful of arugula. Pour the prepared lemon dressing over the ingredients in the bowl. Gently stir everything together so all the flavors distribute well and the arugula stays intact.
Divide the quinoa mixture into a large, deep bowl. Sprinkle the dish evenly with the freshly toasted sunflower seeds. Serve the meal immediately.