Preheat your oven to 350°F (175°C). Grease the muffin tin or line it with muffin liners.
In a large mixing bowl, whisk together the flour, sugar, baking powder, baking soda, and salt until well combined.
In another bowl, mix the sour cream, melted butter, eggs, and vanilla extract until smooth. Pour this mixture into the dry ingredients and stir until just combined. Do not overmix.
In a separate bowl, prepare the cream cheese filling by mixing the softened cream cheese, sugar, and vanilla extract until smooth and creamy.
Fill each muffin cup about halfway with the muffin batter. Add a tablespoon of the cream cheese mixture on top of the batter, and then cover with more muffin batter until the cups are about ⅔ full.
In a small bowl, mix together the sugar and cinnamon for the topping. After filling the muffin cups, brush the tops with melted butter and sprinkle the cinnamon-sugar mixture generously over them.
Bake in the preheated oven for 18-20 minutes or until the tops are golden and a toothpick inserted into the center comes out clean.
Allow the muffins to cool in the pan for about 5 minutes before transferring them to a wire rack to cool completely.