Under 15 Min

In a small bowl, combine the mayonnaise with the lime zest. Season with salt and black pepper. Mix well and set aside.

Have the three salsas prepared and ready to use, and the tostadas within reach.

Season the shrimp and scallops with the salt and pepper. Heat 1 tablespoon butter and 1 tablespoon oil in a very large skillet over high heat. Once the butter has begun to foam, add the shrimp. Cook for 1 or 2 minutes per side, just until nicely seared and browned on the outside but not overcooked inside. Scrape into a bowl. Return the skillet to the heat, add the remaining butter and oil, and once the butter foams, add the scallops. Cook for a minute per side, until the tops and bottoms are browned and the middles are no longer translucent, and remove from the heat. The scallops should be medium rare. As soon as you can handle them, slice thin and set aside.

Spread about a tablespoon of the mayonnaise on each tostada, top with a layer of sliced scallops, a couple of tablespoons of the salsa bandera, and then a layer of the shrimp. Crown with avocado slices. Top the avocado slices with a couple of tablespoons of salsa negra and add apple chiltepin salsita or another hot sauce to taste. Serve immediately, passing more salsa negra around the table for people to add as desired.