Preheat the oven to 350 degrees, and grease your muffin tin very well with melted butter.
To make the strawberry jam: in a small saucepan cook the berries, sugar, cornstarch and water just until the mixture thickens, about two minutes.
In a large mixing bowl, cream together the butter and sugar, and then add the egg.
Sift together the flour, baking powder, baking soda, and salt and then stir them gently in the mixing bowl. Mix until just combined and then add the sour cream and vanilla.
Divide half of the batter between the 24 muffin cups. Then, divide all the strawberry jelly between the 24 cups. Finally, top each of the cups with the rest of the batter.
Bake 10 minutes. Then let them cool in the tin on a wire rack for 5 minutes and then take them out of the pan and let them cool on the rack for 10 minutes.
Dip each muffin in the bowl of melted butter, and then roll each one in the sugar mixed with cinnamon.