Line a 10- by 15-inch pan with foil.
In a 10- to 12-inch nonstick frying pan over medium-high heat, shake sugar often until melted and amber-colored, 8 to 10 minutes.
Pour melted sugar onto foil. Let stand until hard, about 30 minutes. Peel off foil and break caramel into chunks.
With motor running, drop chunks into a food processor and whirl into a fine powder. Or whirl chunks in batches in a blender. Immediately store in airtight container. Powder keeps indefinitely, but absorbs moisture quickly if exposed to air.
Nutritional analysis per tablespoon.