Preheat the oven to 350°. In a large saucepan, combine the butter and brown sugar and cook over moderate heat, stirring, until smooth. Stir in the heavy cream and salt and bring to a boil. Simmer just until slightly thickened, about 3 minutes. Let the caramel cool.
Spread the pecans on a rimmed baking sheet and toast for about 8 minutes, until they are lightly browned and fragrant. Transfer the pecans to a work surface and let them cool. Coarsely chop the nuts, stir them into the cooled caramel and serve.
The topping can be refrigerated for up to 1 week. Rewarm slightly before serving.