Polenta Quick Bread with Lemon and Thyme

INGREDIENTS

• 3/4 cup (1 1/2 sticks) unsalted butter, softened, plus more for pan
• 1/3 cup all-purpose flour, plus more for pan
• 3/4 cup sugar
• 1 tablespoon finely grated lemon zest, plus 2 tablespoons fresh lemon juice
• 3 large eggs
• 1 tablespoon coarsely chopped fresh thyme leaves, plus sprigs for garnish
• 1 cup fine yellow cornmeal (preferably stone-ground)
• 1 teaspoon baking powder
• 3/4 teaspoon coarse salt
• 1/4 cup pine nuts, toasted, half coarsely chopped and half whole