Sesame Rice Balls with Red Pepper Dipping Sauce

Purée bell pepper with vinegar and sugar in a blender until smooth. Transfer to a small heavy saucepan and stir in red pepper flakes. Simmer 5 minutes, then pour through a fine sieve into a bowl, pressing on solids.

Rinse rice in a bowl in several changes of cold water until water is almost clear; drain well in a large sieve. Combine rice and 2 cups water in a 3-quart heavy saucepan and let stand 10 minutes. Cover with a tight-fitting lid and bring to a boil over high heat. Cook at a rapid boil (lid will be rattling and foam may drip down outside of pan) 5 minutes, or until water is absorbed. Remove from heat and let stand, covered, 10 minutes.

Transfer warm rice to a large wooden bowl and sprinkle vinegar over it, a little at a time, while gently tossing with a flat wooden paddle or spoon so vinegar is absorbed and rice cools as it is aerated. Cool to room temperature.