Butter sides of heavy 2-quart saucepan; add sugars, buttermilk and salt.
Cook over medium-high heat 6 to 8 minutes until boiling, stirring constantly with wooden spoon to dissolve sugars.
Cook over medium-low heat, stirring occasionally, 16 to 18 minutes or until mixture reaches soft-ball stage, 234°F on a candy thermometer (or until syrup, when dropped into very cold water, forms a soft ball that flattens when removed from water).
Remove pan from heat.
Add butter; do not stir.
Cool, without stirring, about 20 minutes or until 150°F.
Stir in pecans.
Beat vigorously with wooden spoon 2 to 3 minutes or until candy begins to thicken but is still glossy.
Drop candy by teaspoonfuls onto wax-paper-lined baking sheet.
Let dry until hard.
Store in tightly covered container.