(One of the following is good, although zucchini or carrots make a nice substitution for the fruit: coarsely chopped apples, bananas, cranberries, or cherries)

Grease twelve 2-1/2-inch muffin cups and set aside. In a bowl, beat sugar and butter with electric mixer until well combined. Beat in eggs, sour cream and vanilla.
In another bowl, combine flour, baking powder, salt, baking soda, cinnamon, nuts and fruit. Stir into butter mixture until just moistened (batter should be lumpy.)
Spoon into prepared muffin cups, filling each cup two-thirds full. Bake in a 400-degree oven for 20 minutes or until golden. Cool in muffin cups on a wire rack for 5 minutes. Remove; serve warm.