What to buy: Queso fresco is a mild white cheese that doesn’t melt when heated. It can be found in the refrigerated cheese case of most grocery stores or at specialty cheese shops or Latin markets. If you can’t locate it, feta cheese is a good substitute.
1 large head romaine lettuce, torn into bite-size pieces, washed, and dried
1 large bunch watercress, torn into bite-size pieces, washed, and dried
3/4 cup crumbled queso fresco
For the pumpkin seeds:
Heat oil in a medium frying pan over medium-high heat until shimmering. Add pumpkin seeds and cook, stirring frequently, until popped and toasted, about 1 to 2 minutes. Remove with a slotted spoon to a paper-towel-lined plate. Sprinkle with salt and cayenne pepper and toss to coat; set aside.
For the vinaigrette:
Combine cilantro, lime juice, onion, and salt in a large nonreactive serving bowl. While whisking constantly, slowly add oil in a thin stream until completely incorporated.
For the salad:
Add all ingredients to the bowl with the vinaigrette and toss to coat. Season with additional salt as needed. Sprinkle reserved pumpkin seeds over top and serve.