Make the dressing. Add the lime zest, lime juice, olive oil, and salt to a small bowl or jar and stir to combine.
Assemble the salad. Add the watermelon, cucumber, cotija cheese, red onion, mint, and jalapeño to a large bowl. Pour the dressing on top and gently toss to combine. Serve immediately.
Notes
Cotija cheese: Don’t crumble it too fine. Leaving some bigger chunks gives you a real bite of salty cheese. No cotija? Feta works too.
Jalapeño: Seed it for a mild salad, or leave some seeds in for more heat.
Cucumber: English cucumber doesn’t need peeling. If you use a regular cucumber, peel it first.
Chill first: Chill your watermelon before cutting so the salad is cold right away.
Storage: This salad is best the day you make it. Leftovers keep in an airtight container in the fridge for about a day, though they’ll get waterier as they sit. Give it a stir and serve with a slotted spoon to leave the extra juice behind. To prep ahead, store the chopped fruit and veggies separately and mix the dressing up to a few days early, then toss together right before serving.