Pour olive oil into a large frying pan over medium-high heat. When hot, add onions and cook, stirring often, 5 minutes. Reduce heat to medium-low and cook, stirring occasionally, until onions are golden brown, about 45 minutes total. Season to taste with salt and pepper.
Layer turkey on sandwich roll bottoms and mound with caramelized onions. Drizzle generously with Charmoula Mayonnaise, then add lettuce leaves and roll tops.
Note: Nutritional analysis is per sandwich.