How to Make It
In a saucepan, heat 1 tablespoon of the oil. Add the apple, onion, curry and saffron and cook over moderate heat until the onion is softened, 5 minutes. Remove from the heat and stir in 1 teaspoon of water; let cool.
Scrape the mixture into a mini food processor. Add the mayonnaise and process. Transfer the mayonnaise to a bowl and add the cilantro and mint. Season with salt and pepper, then fold in the crabmeat.
Cut each slice of watermelon into 2 triangles and transfer to 4 plates. Season with salt and pepper and sprinkle each plate with 1 teaspoon of lime juice. Mound the crab salad on the watermelon. In another bowl, toss the arugula with the remaining 1 tablespoon of lime juice and the remaining 2 tablespoons of oil and season with salt and pepper. Arrange the arugula on the plates and serve.