Preheat oven to 350°F (175°C).

Combine tuna, mayonnaise, sugar, pepper, and eggs in a large mixing bowl. Add scallions and grape tomatoes and stir to combine.

Divide mixture evenly among the shells, closing each one tightly, and place seam-side down in a large baking pan. Bake covered for 30 minutes.

Remove from oven and drizzle generously with Caesar dressing. Serve hot or room temperature.