First, make the salsa.
In a medium bowl, toss together the chopped onion, lime juice, and salt.
Let this mixture stand for 15 minutes, stirring occasionally, to allow the flavors to meld.
Afterwards, stir in the diced kiwifruit, cilantro, and jalapeño.
Set aside.
Prepare the chile powder.
In a spice mill or clean coffee grinder, grind the dried New Mexico chiles until they form fine particles, similar in texture to sugar.
Set this aside for later.
Cook the beans.
Heat the olive oil in a nonstick skillet over medium heat.
Add the minced onion, cover, and cook for 5 minutes, stirring occasionally, until softened.
Stir in the black beans, ½ cup of the reserved bean liquid, and 2½ teaspoons of your freshly ground chiles. Use a fork or potato masher to mash the beans directly in the pan, leaving some whole for a great texture.
Continue to cook for 5 minutes, stirring often, until the mixture is thick but still moist.
Assemble and serve.
Place one tostada shell on each of four plates. Carefully spread the bean mixture over each tostada, leaving a small ½-inch border.
Top each with a generous dollop of Greek yogurt (about ¼ cup) and a spoonful of the kiwi salsa (about ¼ cup).
Finish with a final dusting of the ground chiles and serve immediately with any remaining salsa on the side.
When mashing the beans, don't overdo it! Leaving some beans whole creates a wonderful, rustic texture that's much more satisfying than a completely smooth purée.
