In a large skillet over medium heat, melt 2 Tb of the butter. Add chicken and shrimp. Sprinkle with salt and pepper. Cook stirring frequently until chicken is light golden and shrimp are pink, about 4 minutes. Remove chicken and shrimp; set aside. To skillet add peppers; cook until crisp-tender. Break up tomatoes in the can. Add to skillet; heat until bubbling. Add chicken and shrimp. Stir in remaining 2 Tb butter, 1 Tb at a time, until just melted. Arrange pasta on platter; top with chicken-shrimp mixture.