YUCATECOS LIVE in a tasty world of bright flavors. The natural sweetness of ripe tomatoes invigorated with the ignitable potential of habanero, the aroma of cilantro, the zing of sour orange or lime, and the resonant crunch of raw radish and onion. That's xnipec (say "shnee-pek," Mayan for "nose of the dog" the books say, refraining from further comment). If you leave out the tomatoes, most Yucatecos call the resulting mix salpicón, an enlivened sprinkle for their otherwise quite simply flavored fare. I doubt you'd think of the tomatoless version as a salsa (especially one for chips), but its possibilities as a relish are numerous.
 

MAKES ABOUT 2 CUPS

 

• 1 small (4-ounce) red onion
• 2 tablespoons fresh sour orange or lime juice
• 10 ounces (2 small round or 3 or 4 plum) ripe tomatoes
• 6 radishes
• 1/2 to 1 whole fresh habanero chile, depending on your personal attraction to the "burn"
• A dozen or so large sprigs of cilantro
• Salt, about 1/2 teaspoon

Very finely chop the onion with a knife (a food processor will make it into a quickly souring mess), scoop it into a strainer and rinse under cold water. Shake off as much water as possible, then transfer to a small bowl and stir in the juice to "deflame" the onion's pungency. Set aside while you prepare the remaining ingredients.

 Core the tomatoes, then cut them crosswise in half and squeeze out the seeds if you want (it'll make the sauce seem less rustic). Finely dice the tomatoes by slicing them into roughly 1/4-inch pieces, then cutting each slice into small dice. Scoop into a bowl. Slice the radishes 1/16 inch thick, then chop into matchsticks or small dice. Add to the tomatoes. Carefully cut out and discard the habanero's seed pod (wear rubber gloves if your hands are sensitive to the piquancy of the chiles), mince the flesh into tiny bits, and add to the tomatoes. Bunch up the cilantro sprigs, and, with a very sharp knife, slice them 1/16 inch thick, stems and all, working from the leafy end toward the stems.

 Combine radishes, chile, and chopped cilantro with the tomato mixture, stir in the onion and juice mixture, taste and season with salt, and it's ready to serve in a salsa dish for spooning onto tacos, grilled fish, and the like.
 

ADVANCE PREPARATION -- The salsa is best within a few hours of its completion, and be forewarned that the longer it sits, the more picante it will seem.