– Heat the oil in a skillet over medium-high heat. Add the onions and the garlic and cook for about 3 minutes, until the onion becomes transparent.
– Stir in the tomato, chipotle pepper, and oregano and cook for about 8 minutes, until the tomato has cooked and released its juices.
– Add the tuna and cook for 5 more minutes. Season with salt and pepper.
– To assemble the tostadas, spread about a tablespoon of beans on the tostada, then top with the tuna tinga and some shredded lettuce. Sprinkle with a small amount crumbled queso fresco and drizzle with few drops of cream.