Preheat oven to 350°F. Lightly butter 8 muffin tins or line with paper muffin liners and set aside.
Combine flour, sugar and baking soda in a large mixing bowl. Add egg, 1/2 tsp. vanilla, walnuts and pineapple. Beat with an electric mixer until thoroughly combined.
Fill muffin tins 2/3 full with batter.
Bake about 25 minutes or until tester comes out clean when inserted in center. Let cool 5 minutes before turning out onto a rack. Sprinkle top of cupcakes with confectioner's sugar.