Drain the corn well.
Cut the cucumber, bell pepper and tomatoes into half-inch pieces.
Finely slice the red onion.
Toss the corn, cucumber, bell pepper, tomatoes and onion with salt and pepper.
Stir the lemon juice and melted butter together. Add to the vegetables. Toss well. Taste. Add more salt and pepper, if needed.
Toss in the cilantro.
Serve at room temperature.