Melt butter in a skillet over medium heat; cook chicken in the melted butter until browned, 3 to 4 minutes per side. Transfer chicken to a plate. Add tomatoes with green chile peppers, water, tomato sauce, and Spanish-style rice mix to the same skillet; stir well. Return chicken to the rice mixture and bring to a boil. Reduce heat, cover skillet, and simmer until chicken is no longer pink in the center and rice is tender, about 40 minutes. Serve on a platter with chicken atop the rice.