Step 1Combine watermelon, feta and jalapeno in serving bowl.
Step 2Toast the cumin seeds in a dry pan over medium heat until they become fragrant and begin to pop, about 2 minutes. If using a mortar and pestle, grind the cumin seeds to dust, add lime juice, salt to taste and oil and whisk to a smooth emulsion. If using a blender, combine the cumin seeds, lime juice, salt and oil and blend until smooth.
Step 3Just before serving, add half of the dressing to the watermelon mixture. Toss gently to keep everything whole and taste the salad. If desired, add more dressing. Add the chopped mint and toss gently.