Whisk 1/4 cup lemon juice, 3 tbsp canola oil, 2 tbsp soy sauce, 1 tbsp toasted sesame oil, 11/2 tbsp sugar and 11/2 tbsp minced fresh ginger in a small bowl.
Combine 3 tbsp of the dressing with 2 cups tuna,1 cup sliced peas and 2 sliced scallions in a medium bowl.
Divide cabbage among 4 plates. Mound one-fourth of the tuna mixture (about 1/2 cup) in the center of each plate and garnish with radishes, cilantro and sesame seeds. Drizzle with the remaining dressing (about 2 tablespoons per salad) and season with pepper.
The curry is ready. Serve hot with tapioca and enjoy!