Blue Corn Tostadas with Yellowfin Tuna, Avocado, and Cucumber

I love serving yellowfin (ahi) tuna raw because of its buttery texture, beautiful red color, and mild flavor. Here, it is used with ingredients typical of aguachile (see page 171), Mexico’s answer to ceviche, so it works beautifully on a crunchy, golden tostada. Be sure to purchase “sushi-grade” tuna for all raw preparations and use it within a day or two of purchase. You can swap out the blue corn tostadas for white or yellow tostadas.