1. Preheat oven to 425 degrees. Spray muffin tin with nonstick cooking spray or line with liners.
2. Bring one cup blueberries and one teaspoon sugar to simmer in small saucepan over medium heat. Cook, mashing berries with spoon several times and stirring frequently, until berries have broken down and mixture is thickened and reduced to 1/4 cup. Let cool to room temperature.
3. Whisk flour, baking powder, and salt together in large bowl.
4. Whisk together sugar and applesauce, then slowly whisk in cooled butter and oil until combined. Whisk in yogurt mixture and vanilla.
5. Fold wet ingredients and remaining blueberries into dry ingredients until just combined. Do not overmix.
6. Fill muffin cups to the top and, using a chopstick or skewer, swirl in one teaspoon of cooled blueberry jam. Bake for 17-19 minutes. Let cool for a few minutes in pan before moving to a wire rack.