In a large bowl, mix together sour cream, 1/2 cup sugar, salt, and yeast. Stir until yeast dissolves. Add eggs, 1/2 cup melted butter, and half of the flour; mix well. Mix in the remaining flour.
Turn dough out on floured board. Knead until smooth, about 10 to 15 minutes. Place in greased bowl, and cover. Let rise in warm place until double in bulk, about 1 1/2 to 2 hours. Punch dough down. Turn over, and let rise again for 45 minutes.
Place 1/2 cup melted butter in a small cup. Mix together 1 cup white sugar, chopped nuts, and cinnamon. Form dough into walnut-sized balls. Dip each ball in melted butter, and roll in sugar-nut mixture. Place in layers in a 10 inch greased tube pan. Sprinkle any remaining sugar-nut mixture or melted butter over the top layer of balls. Cover pan with waxed paper and a towel, and let dough rise again 45 minutes.
Bake at 375 degrees F (190 degrees C) for 40 to 50 minutes, or until golden brown. Run a spatula around sides of cake, and invert onto plate.