In a large bowl, combine the sugar, flour, cherries, sour cream, egg and extract. Spoon into the pastry shell. Bake at 400° for 20 minutes.
For topping, combine the oats, flour, brown sugar and cinnamon in a small bowl; cut in butter until mixture resembles coarse crumbs. Stir in pecans. Sprinkle over filling. Cover edges of crust to prevent overbrowning.
Bake for 25-30 minutes or until topping is lightly browned. Cool on a wire rack for 1 hour. Store in the refrigerator. Yield: 8 servings.