In a large saucepan over high, combine the chickpeas and their 2 cups reserved liquid, the baking soda, ½ teaspoon salt and 3 cups water. Bring to a boil, then reduce to medium and cook, uncovered and stirring occasionally, until very tender and the chickpea skins begin to fall off, 15 to 20 minutes.

Meanwhile, in a food processor, combine the black beans and their 2 tablespoons reserved liquid, 2 tablespoons of lime juice, the cumin, the chipotle chili and adobo sauce, and ¼ teaspoon each salt and pepper. Process until smooth, scraping the bowl as needed, 20 to 30 seconds. Add ¼ cup of the cilantro and pulse 2 or 3 times to combine. Transfer to a medium bowl, then taste and season with salt and pepper; set aside. Wipe out the food processor.

When the chickpeas are done, drain them in a colander set in a large bowl. Reserve ¾ cup of the chickpea cooking liquid; discard the remainder. Let the chickpeas drain for about 1 minute, shaking the colander to drain as much liquid as possible. Add the warm chickpeas to the processor along with ½ teaspoon salt. Process until completely smooth, about 3 minutes. Add the tahini and continue to process until the mixture is lightened and very smooth, about 1 minute. Scrape the sides and bottom of the processor bowl. With the machine running, add the reserved cooking liquid and 4 tablespoons (¼ cup) of the remaining lime juice, then process until well combined, about 1 minute. Taste and season with salt.

Transfer the hummus to a shallow serving bowl. Spread the black bean mixture on top in an even layer. Wipe out the bowl used for the black beans, then add to it the tomatoes, onion, jalapeño, the remaining 2 tablespoons lime juice and ¼ teaspoon salt; stir to combine.

Distribute the tortilla chips over the black-bean layer and spoon the tomato salsa on top. Sprinkle with the remaining ¼ cup cilantro and serve immediately.