How to Make It
Place fish in a medium-size nonreactive bowl. Add lime juice; gently fold to combine, making sure fish is covered with juice. Cover and chill until fish is opaque and firm, about 30 minutes.
Drain and discard liquid. Gently fold in tomato, radishes, orange juice, chile, and salt. Top with cilantro and pepitas, and, if desired, sprinkle with salt to taste. Serve immediately with plantain chips.