Place beans in a large pot of boiling salted water and cook until tender, about 8 minutes. Drain and rinse under cold water.
In a large skillet, warm butter over medium-high heat until golden brown, 3 to 5 minutes. Add pecans and cook, stirring, until lightly toasted, 2 minutes. Add beans, season with salt and pepper and cook, stirring, until heated through, 2 minutes. Transfer to a serving platter. Serve hot.