Heat butter in pan over med heat til melted. Add onion, oregano, and 1/2 tsp salt; cook, stirring occasionally, untl liquid has evaporated and onion golden brown--about 5 min. Add garlic and cook until fragrant-about 30 sec. Stir in tomatoes and sugar, increase heat to high and bring to simmer. Lower heat to med-low and simmer til thickened slightly-about 10 min. Off heat, stir in basil and oil; season with salt/pepper. Serve over pasta. Makes 3 cups-enough for 1 lb pasta.