In A Skillet Over Medium Heat, Brown The Ground Beef With The Onion, Until The Meat Is No Longer Pink, And The Onion Is Soft; Drain Fat. In A Dutch Oven Or Large Saucepan, Combine The Ground Beef Mixture, And Pureed Tomatoes. Season With Worcestershire Sauce, Chili Powder, Salt And Pepper. I Just Keep Adding Stuff Until It Tastes Good. Bring To A Boil, And Let Simmer For 15 To 20 Minutes To Blend Flavors. Serve Over Rice.