In medium bowl, toss together mango, red bell pepper, shallot, 2 tablespoons lime juice, cilantro, 1/2 teaspoon salt, and 1/8 teaspoon cayenne; let stand at room temperature to blend flavors, 15 to 30 minutes. Adjust seasoning with additional lime juice, salt, and cayenne; stir in pepitas and serve.

Makes about 3 cups