How to Make It
Preheat oven to 350°. Beat butter at medium speed with a heavy-duty electric stand mixer until creamy. Gradually add granulated sugar and brown sugar, beating until light and fluffy. Add eggs, 1 at a time, beating at low speed just until blended after each addition.
Stir together flour and next 4 ingredients in a small bowl; add to butter mixture alternately with sour cream, beginning and ending with flour mixture. Beat at low speed just until blended after each addition. Stir in pecans, apples, and vanilla.
Spoon batter into well-greased (with cooking spray) muffin pans, filling three-fourths full. Sprinkle about 1 Tbsp. Pecan Streusel over each muffin.
Bake at 350° for 22 to 25 minutes or until a wooden pick inserted in center comes out clean. Cool in pans on wire racks 5 minutes; remove from pans to wire racks, and cool 15 minutes.