Preheat oven to 350°. Line a 12-cup muffin pan with paper liners.
For streusel: In a medium bowl, stir together cornmeal, flour, brown sugar, and pecans. Add melted butter, and stir with a fork until combined. Freeze until ready to use.
For muffins: In a medium bowl, whisk together cornmeal, brown sugar, flour, cinnamon, baking soda, and salt.
In a large bowl, whisk together eggs, applesauce, butter, sour cream, and vanilla.. Fold cornmeal mixture into applesauce mixture just until combined. Fold in diced apples and pecans. Spoon batter into prepared muffin cups. Top with streusel.
Bake until a wooden pick inserted in center comes out clean, 22 to 25 minutes.
Recipe by Taste of the South at https://tasteofthesouthmagazine.com/apple-cornbread-muffins/