Combine The First Five Ingredients; Rub Over Chicken. In A Nonstick Skillet, Brown Chicken In Oil On Both Sides. Add Onions, Jalapeno And Garlic; Saute For 1 Minute. Add Tomatoes; Bring To A Boil. Reduce Heat; Cover And Simmer For 15-20 Minutes Or Until Chicken Juices Run Clear. Remove Chicken And Keep Warm. In A Small Bowl, Combine Cornstarch And Water Until Smooth; Stir Into Tomato Mixture. Bring To A Boil; Cook And Stir For 1 Minute Or Until Slightly Thickened.