Heat oven to 400 degrees. Grease bottom only of 12 muffin cups.
Place milk, pumpkin, eggs, and oil in medium bowl. Mix flour, ¼ cup sugar, the baking powder, salt, cardamom, ½ teaspoon cinnamon, and the nutmeg. Stir into liquid mixture until thoroughly moistened.
Fill muffin cups evenly. Brush tops lightly with melted butter.
Mix walnuts, 3 Tablespoons sugar, and ¼ teaspoon cinnamon. Sprinkle muffins with nut mixture.
Bake until golden and until a pick inserted in center comes out clean, about 16 to 22 minutes. Remove and cool on wire rack.
Recipe by The Culinary Cellar at https://theculinarycellar.com/pumpkin-muffins-cardamom/