Heat the oven to 425 degrees. Line a baking sheet with parchment paper. In a large bowl, stir together 2 tablespoons Tajín, the baking powder and 1½ teaspoons salt. Add the wings and toss until the spice mix is absorbed into the chicken. Spread the wings in an even layer on the prepared baking sheet. (You can let the wings sit out at room temperature for up to 1 hour after coating, or in the refrigerator overnight. Let them come to room temperature before proceeding.)
Roast the wings until golden and crisp all over, turning the wings over halfway through, about 25 minutes per side.
When the wings are just about done, add the butter, the remaining ½ tablespoon (1½ teaspoons) of Tajín seasoning, and the paprika to a small bowl or microwave-safe measuring cup. Microwave in 30-second bursts until the butter has melted. Stir to combine, then add the lime juice, garlic, and serrano (to taste). Season with salt to taste.
Transfer the wings back to the cleaned-out large mixing bowl. Pour the buttery sauce over the wings and toss to coat. Serve alongside the jicama, cucumbers, and pineapple, if you like, with a little more Tajín sprinkled over everything.
