Heat oil in a heavy, medium-sized skillet over medium heat. Add onions and stir-fry until onions turn caramel brown, about dozen to 15 minutes. Remove from heat. Place in a blender with the ginger, tomatoes, cilantro, cayenne and salt; puree until smooth. Transfer to a medium-size saucepan. Stir in garam masala or curry powder, cover, and cook over medium heat until tomatoes loose their raw aroma, 15 to 18 minutes. Makes about 2 cups. PER TABLESPOON: 15 calories, 0 g protein, 1 g carbohydrate, 1 g fat (0 g saturated), 0 mg cholesterol, 69 mg sodium, 0 g fiber. Laxmi Hiremath writing in the San Francisco Chronicle, 0. 0.27173913043478.