Make the salsa
Prepare a high gas or charcoal grill fire. In a small bowl, combine 1 tsp. of the olive oil with the ground chipotle. Brush the watermelon slices on both sides with the chipotle oil and sprinkle with 1/4 tsp. salt. Grill the watermelon until charred spots appear on both sides, about 1 minute per side. Transfer to a cutting board. When cool enough to handle, remove the rind, seed if necessary, and coarsely chop the flesh.
In a food processor, combine the watermelon flesh, tomato, cucumber, cilantro, shallot, serrano, and the remaining 3 tsp. olive oil. Pulse until the ingredients are mixed but still chunky. Transfer the salsa to a medium bowl and stir in the lime juice. Refrigerate to let the flavors meld, about 1 hour. Just before serving, season to taste with salt
Make the Chips
Heat the canola oil in a 10-inch straightsided skillet over medium-high heat. (You should have about 1/2 inch of oil.) Stack the tortillas and cut the stack into 6 wedges. In a small bowl, combine the lime zest with 1 1/2 tsp. salt. With your fingers, rub the salt and zest together until the salt is seasoned and the zest is broken into very small pieces. Stir in the cayenne.
To test the oil, add a small piece of tortilla. If it sizzles immediately, the oil is ready; if it sinks, wait another minute and test it again. When the oil is ready, add a handful of tortilla triangles (about 15) and cook until lightly browned and crisp, turning halfway through with a slotted spoon, 1 to 2 minutes. (If the tortillas seem to brown too quickly, reduce the heat.) Transfer the chips to a plate lined with paper towels and drain for 2 minutes. Put the warm chips in a clean paper bag, add 1/8 tsp. of the seasoned salt, close the bag, and shake gently. Season with more salt to taste. Repeat with the remaining tortillas. Serve the salsa with the chips.
Make Ahead Tips
The salsa and chips may be made up to 1 day ahead. Refrigerate the salsa, and store the chips in an airtight container.
nutrition information (per serving):
36, Fat Calories
310, Saturated Fat
2, Monounsaturated Fat
27, Polyunsaturated Fat
Photo: Scott Phillips