Rinse the tuna, pat dry, and cut into small cubes.
Peel the shallot and apple. Remove the core from the apple, and finely dice the shallot. Mix the tuna, lemon juice, and 1 tablespoon of olive oil. Season to taste with salt and pepper. Place the roses on a plate, and using a ring mold, form the tartare over the top. Drizzle with olive oil, garnish with a dab of mayonnaise, and serve.