Preheat oven to 375°F. Spray a 12-cup muffin tin with nonstick spray.
In a medium bowl, whisk together the flour, sugar, baking powder, cinnamon and salt. Make a well in the center of the flour mixture. In a separate bowl, whisk together the yogurt, butter, milk, egg and vanilla. Add the yogurt mixture to the flour mixture, stirring just until moist.
Spoon 1 tablespoon of batter into each muffin cup. Top each with 1 teaspoon of jam. Top evenly with the remaining batter. Combine the sugar and cinnnamon; sprinkle over the tops of the muffins.
Bake for 15 minutes or until a toothpick inserted into the center comes out clean. Cool in pan on a wire rack 10 to 15 minutes. Remove from pan; place on a wire rack. Store muffins in a covered container. They are best eaten within a day or two.