This Shrimp Ceviche Tostada with Fennel and Grapefruit is a refreshing and flavorful dish that combines the tangy flavors of citrus with the delicate sweetness of shrimp. The ceviche is made by marinating the shrimp in a zesty mixture of lime juice, grapefruit juice, and cilantro. The fennel adds a crunchy texture and a hint of licorice flavor, while the grapefruit adds a burst of freshness. Serve this ceviche on top of crispy tostadas for a satisfying and light meal.