Spicy Tuna Tostada

Name: Spicy Tuna Tostada
Ingredients: 2 to 3 cups vegetable oil; Eight 4-inch corn tortillas; 12 to 16 ounces number 1 grade ahi tuna; 3 tablespoons extra-virgin olive oil; Kosher salt and freshly ground black pepper; 1 shallot, finely minced; 1 lime, cut into supremes (see Cook's Note), juice reserved; 1 watermelon radish, peeled, or 4 regular radishes, julienned; 1/2 bunch fresh cilantro, leaves picked, stems discarded; 2 to 3 chipotles in adobo sauce; 1/2 cup mayonnaise; Juice of 1/2 lime; 1/8 cup pure olive oil; Kosher salt