Tuna Ceviche Tostadas with Chipotle Crema

Ingredients

• 2 cups neutral oil, such as vegetable, canola, or grapeseed
• 8 corn tortillas
• Fine sea salt
• 1 pound ahi or bluefina tuna, cut into 1/2-inch cubes
• 1/2 cup thinly sliced red onion
• 1/2 cup fresh lime juice
• 1/4 cup mayonnaise
• 1/4 cup sour cream
• 1 chipotle chile in adobo sauce, deseeded and finely minced
• 1 small papaya, cut into 1/2-inch cubes (about 1 1/2 cups)
• 1 avocado, cut into 1/2-inch cubes
• 1/4 cup coarsely chopped cilantro, plus more for garnish
• 1 serrano chile, thinly sliced (optional)