Preheat the oven to 425° and place muffin liners in a muffin pan. Spray with nonstick cooking spray.
Combine the flour, baking powder, baking soda, cinnamon, nutmeg, and salt in a mixing bowl.
In a large bowl, cream the butter, sugar, and brown sugar till creamy.
Add the eggs and beat for another 30 seconds.
Beat in the milk, sour cream, and vanilla until combined.
Mix in the dry ingredients to the wet ingredients just till combined.
Do not overmix or the muffins can become dense.
Fill the cupcake liners even with the top.
Place in the oven and bake for 5 minutes. After 5 minutes, reduce the heat to 350° and continue baking for 15 minutes till a toothpick inserted comes out clean.
Combine the sugar and cinnamon together in a small bowl.
Brush one of the muffins with melted butter, then roll in the cinnamon sugar. Repeat until all the muffins have been rolled in the cinnamon sugar.
Fill a piping bag with a large circle tip, with the cajeta, then press the tip into the center of the muffin and pipe the cajeta into the muffins. Or, drizzle the cajeta over the tops.
Serve with coffee or milk for a delicious snack.
Notes
Store in an airtight container in the refrigerator for up to 5 days.