3⁄4 cup (1 1⁄2 sticks) unsalted butter
1 cup granulated sugar
1 tablespoon finely chopped fresh sage leaves
1 cup packed light brown sugar
2 1⁄2 cups unbleached all-purpose flour
1 can (15 ounces) pumpkin purée
2 teaspoons baking powder
3 large eggs
2 teaspoons ground ginger
1 teaspoon pure vanilla extract
1 teaspoon salt
1 cup chopped walnuts
Preheat the oven to 375ºF. Grease a 12-cup Bundt pan and dust with flour. Combine the butter and sage in a small pan and heat on low until the butter is melted. Set aside to cool.
Whisk together the flour, baking powder, ginger, and salt in a medium mixing bowl. Whisk together the butter and sage mixture, granulated sugar, brown sugar, pumpkin, eggs, and vanilla in a large mixing bowl.
Stir the flour into the pumpkin mixture until combined. Stir in the chopped nuts.
Scrape the batter into the prepared pan. Bake until a toothpick inserted in the center comes out clean, 40 to 45 minutes. Let cool in the pan for 5 minutes, then invert it onto a wire rack to cool completely. Slice and serve.
Store uneaten cake in a cake keeper or wrap in plastic and store at room temperature for up to 3 days.