Finger-lickin’ Cajun chicken

Melt butter in a large, wide frying pan over medium-high. Sprinkle chicken on both sides with Cajun seasoning. Add to pan. Cook, uncovered, until chicken is golden and cooked through, 4 to 5 min per side. Transfer chicken to a platter and cover loosely with foil. Drain all but 1 tbsp oil from the pan and return to heat. Add tomatoes. Using a wooden spoon, scrape up and stir in any brown bits from pan bottom. Reduce heat to medium-low. Cover and simmer, stirring occasionally, until tomatoes start to break down and turn saucy, about 5 min. Stir in onions for the last 3 min of cooking. Serve sauce over chicken.